when you are using 4gb out of 4gb you are using too much and it likely crash i guess

with 2gb i had no way to even catch up this game. it ate 1.5gb out of 2.0gb and that's all. zero-fps.

What does this map do to create a crash?

I played Epic which is 40x40 some Spring versions ago and nevercrashed on it. That map doesn't have any default features though.
I played it on my old computer before you could rejoin games. Worked well.

I've crashed in other big games than Zero-K like NOTA with Std:bad alloc as message.
Crashes happens quite often in Spring now it seems compared to back then. Being able to rejoin games might have caused people to trivialize crashes.

Std:bad alloc also occured to me when taking tons of screenshots in short time (like keeping the hotkey pressed).

This map is a crash fest. Only notepad likes it and constantly puts it forward. The basic problem with this map is that it promotes the use of lots and lots of cheap fast units (fleas, avengers, glaives, gnats, blastwings). I played it twice, I think, with crashes all around (not just me, almost everyone). One std::bad_alloc, one something else.