> all the NATO trainings occurred during the war, after Russian aggression against Ukraine began.

Wrong. NATO had at least one Partnership for Peace exercise in Ukraine in October 2002, a few hours drive from L'Viv.[1]

And just to be specific; this doesn't justify any aggression on Russia's behalf, sovereign nations are free to decide who to ally with.

[1] - https://www.nato.int/ims/2002/p021007e.htm