How on earth is that first queen sac justified

This defies my mortal understanding.

Wow, that's an intense game. I'm also interested in that queen sac, even though white ended up losing his own queen to keep his king protected later in the game.

Fritz, just a quick analyses:

24. d5?? (leading to quick end)

No comments (!) about either of the queen sacs, though infinite analyses justifies the first, commending it as the first option and goes against second, where white returns the queen and goes from +0.6 to -1.2

What's wrong with 18. Kg3?

isnt Nezhmetdinov known for is intense aggressive style with a lot of queen sacrafices? His games is just awsome...

black is giving up his queen for at least two bishops a pawn of material (if he even wants the second bishop!) that's about a two pawn material plus for white.  black in return gets a nice looking attack that does seem to be at least enough compensation for the material given up.