What do you think of the Crimean water crisis (with Ukraine as its main source) as a cause for Putin hurriedly invading Ukraine? It's the only reason I can find that actually explains why this is happening now instead of another day.

I understand the why of it, as Putin taking a weird Nazi stance of trying to reunite his people (by murderously destroying anyone who doesn't share that goal, rather than murdering people already outside that racist definition like Hitler did).