This is a shit load of code, serious devs capable of doing this would be doing something that paid them instead.
That's just not true. There's plenty of passion projects out there of people hand decompiling code for massive games.
Decompilations and emulators have been a thing long before LLMs even existed.
Which is why we have playable Ocarina of Time remake emulators and decomps within 2 or 3 days all of a sudden.
No, we have Ocarina of Time emulators and decomps within 2 or 3 days because the yuzu folks spent years reverse engineering and documenting every detail about the Switch 1.
The Switch 2 is so similar to the Switch 1, the first proof of concept Switch 2 emulator is 95% just Eden/yuzu. Things would have taken much longer if yuzu didn't exist, even with LLMs.