It wasn't Hood's 12 inch hull armor that failed her. It was her 3 inch deck armor. The Bismarck sunk the Hood by plunging fire, meaning it was raining shells down from above. Instead of shooting at her side.

And IIRC, the magazine that got detonated was one that would've been removed had Hood received her planned refit. She still would've been at a disadvantage against Bismarck, but just look at everything Warspite survived. A properly refitted Hood would've been similarly protected (still no guarantee of survival, but it certainly would've increased her odds), but she was considered too valuable to take out of service long enough and just got a half-assed refit where the 5.5 inch secondary guns were replaced by 4 inch AA guns.

Magus said:

And IIRC, the magazine that got detonated was one that would've been removed had Hood received her planned refit. She still would've been at a disadvantage against Bismarck, but just look at everything Warspite survived. A properly refitted Hood would've been similarly protected (still no guarantee of survival, but it certainly would've increased her odds), but she was considered too valuable to take out of service long enough and just got a half-assed refit where the 5.5 inch secondary guns were replaced by 4 inch AA guns.

Consider also that Hood had been run absolutely ragged by the RN due to her speed in the interwar period. She was literally falling apart in some places before Bismarck blew her up.