You can't justify the war with actions taken before the war either, the technical term for that is "unjustifiable".

But what the Ukrainian politicians then did wasn't sensible. They've been broken. They have some of the poorest political leadership we've seen out of any country so far in the 21st century. They've managed to transition their country from comfortable and improving to a smouldering wreck. At every turn they've managed to find an option that leaves them unambiguously worse off than they were before. It is a case study in diplomatic failure and what not to do when threatened by a larger, more militarily competent neighbour.