I don't really think Grandfather lost control of the Droyne.
IMTU he gave control up.
It's a crucial difference - he didn't give it up because he couldn't handle it, he gave it up because he didn't want it. To me Grandfather is sort of like the stereotypical Chinese wise man on the top of the mountain - except he lives in a pocket universe instead of a mountain for his solitude. In his quest for wisdom and knowledge about the "human condition" (or the Droyne Condition) he's growing ever further away from very condition he seeks to know about. He's basically reached the stage in Chinese mythology where the wise man no longer needs to eat or drink, he can just sip the clouds for his transcendent metabolism. Grandfather really isn't Droyne. He is a species with just one member - hismelf. In fact, I consider him an entirely different order of life from the rest of us oxygen breathers - he's Retired. He's discovered truths and things that are so distant from our understanding what he knows, he can no longer explain to us we simply don't have the context to understand him nor could we gain such context without living for a few thousand years. Nevertheless, he could predict things in the universe using his knowledge and would be right - he's not insane. He doesn't need to learn your language to speak with you. Using his psionic skills and his knowledge of thinking processes common to all sentient races, he just speaks his language and somehow you translate it perfectly into your own language - only if you recorded it and listened to it later would you hear the jibberish. Say one of your party members is nursing a broken heart from a lover or a dead loved one. Grandfather could simply say a few words, and they'd be the perfect words to comfort them and make the let go of the pain. Truths like that, if he cared to do such things. It's just he's just so far beyond us that things like jobs, taxes, aging, children, social justice, and so on are meaningless to him.
But like any good parent, he saw to it that his children, the Droyne, are as well taken care-of as he can manage - he's done that with the Coyns where the Droyne can manage their own future by polling the collected wisdom of their race in a sort of "grand psionic democracy" of the coyn rituals. It's not precognition, though it seems like it. It's more like tapping the knowledge of all the Droyne to make decisions. For instance, how often in a group of humans is a decision made, only later it comes out that someone had relevant information that could have led to a better informed decision, be it an observation, knowledge, or an opinion that somehow doesn't get shared. Perhaps the person just doesn't like to speak up, they don't think it's relevant, or they keep it back for some purpose of their own. With coyn rituals, this doesn't happen - it taps the knowledge of all the Droyne to make a decision. So often the decision will be influenced by knowledge held by Droyne that aren't even immediate to the situation but still has relevance. For instance, some group of Droyne might be aware of a great invasion of Guild mercenaries killing all of the Droyne on a planet. However, news of this is still months away from where the players and the Droyne doing the ritual are and to them, the Droyne colony seems overpopulated and instead of the decision of "extinguish" which is what the Droyne and their human friends were expecting, the life change draw of the coyn votes "Path of the Warrior." Only months later does the truth of the draw come true and it seems like precognition to the players, but it's really just polling the wisdom of all the Droyne.
Perhaps Grandfather left other helpers, like some of his super-advanced robots living hidden lives amongst the Droyne, but I'd doubt it - as heartbreaking as it is to a parent, another thing a good parent needs to know is when to let go of their children and let them stand on their own two feet. Coddling them forever will just stunt their growth.
Plus, Grandfather is feeling a beckoning...a pull. Grandfather is nearing the end of membership in the Oxygen life order, about to move to the Retired order and already in his researches and information he's starting to see certain patterns that only someone of his age and wisdom can understand. A certain sort of breadcrumb trail, an invitation from those ancient races that "Retired" long before he was born, leaving esoteric clues out for those who reach the same place in the future to come find them. They'll be delighted that Grandfather invented Jump Drive, but as Grandfather's learned (and they learned millions of years before him) you ultimately do the most important travelling without moving at all - they transcended without Jump Drive. Grandfather's a little nervous of them right now, but eventually (perhaps tomorrow or in a few thousand years -- time as we know it is meaningless for him now that he's perfected the technology to exist comfortably just outside of the Event Horizon of his own black hole), he'll seek them out because for once, even beyond his own children, he'll finally meet patience, ancient intelligences whom he can speak to as his peers in intelligence, wisdom, and vision, and he'll finally find a place in a community as a member instead of a godlike head.
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As for the Virus, their future is not entwined with the Droyne alone. I'm follow David Brin's Uplift Universe with its multiple orders of sentient life. The Virus represents the creation of an entirely new and different order of life - the Machines. We're already familiar with Oxygen breathers (which are most Traveller races), but in T4 we also learned about at least one of the Hydrogen breathers.
The birthing pains of this new order of life was the end of the Final War and it's still going on. It'll probably go on for centuries yet before oxygen life and machine life come to an accord. There'll be conflict, hatred, suspicision, and plenty of genocide. I see the hatred that most Traveller players feel towards the Virus as the exact kind of resentment and fear of the future that the established races would feel at the sudden realization they might be sharing a universe with a new race that wasn't there before. "What can we expect?" "Everything."
The appearance of the "machine" icon on the coyns isn't the sign of some special link between Droyne and the machines. It's a sign that the Virus is not just some data error or some temporary abberation, or some "rarely encountered weirdness" as Nilsen himself counseled. It's that there's a new race on the block, and it needs to be taken into account as much as any other race in the Traveller universe, no more, no less.
