I remember that too. Three very good men died in that fire.
Whenever this comes up, I'm moved to reflect on the 3 major "space" movies. "The Right Stuff", "Apollo 13", and "From the Earth to the Moon (FtEttM)".
Now, this is all taken as presented in the movies - how those reflect reality, I just can't say. I simply take them at their word.
In "The Right Stuff", Grissom was portray very poorly when the Mercury capsule was lost. The fundamental point of contention was that The Powers That Be blamed Grissom for the "blown hatch", whereas Grissom contended that the hatch "just blew". That he explosive bolts system securing the hatch failed somehow.
In TRS, it was mentioned how explosive bolts had been tested in aircraft for years, and never "just blew". Grissom was portrayed as being in disgrace.
In Apollo 13, Hanks as Lovell talked to his son about the Apollo 1 fire. About how there was a problem with the door, and reassured his son that they had fixed the door, so that his Dad wasn't in the danger the Apollo 1 crew was.
In "FtEttM", talking about the Apollo 1 fire, one of the folks was talking about the Apollo 1 hatch. The Apollo 1 hatch not only was oriented wrong (opening inward, instead of outward), it did NOT have explosive bolts. It did not have explosive bolts because, after analysis of Grissoms Mercury incident, it was ascertained that, indeed, the bolts apparently DID "just blow". They "just blew", and that was considered a risk on the Apollo capsule. If that did not happen, if they did not "just blow", if Grissom was not (apparently) disgraced by the event, Apollo 1 would likely have had the mechanism in place, that the crew could have used to potentially save their lives.
As the character in the episode said "I'm not a real fan of irony".
Peace to the crew, and their families.