I was blissfully unaware ... playing outside in the snow, no doubt. Or perhaps playing "vroom-vroom" with my Christmas presents.
Once I did learn about it, I was amazed at the apparent stupidity of pressurizing the capsule with pure oxygen. "Duh, what do you expect to happen?" But there was a very good reason, with pure oxygen, it was possible to reduce the cabin pressure considerably, reducing capsule mass and stress on the pressure compartment. The Russians had also lost a cosmonaut to this same problem six years earlier, but due to Cold War tensions and secrecy, we in the west never learned about this until decades later.
Sadly, the crew didn't die instantly, although I'd prefer if you were correct. They attempted to battle the blaze, and may have attempted to escape. NASA's Apollo 1 Fire Timeline
is thorough with details ... starting at 23:31:04, the crew became aware of the problem.