Obviously peace is the ideal, but it's clear who the more agressive party is, the article is not about them, peace is also always bilateral. For Finland this is not about ignoring diplomacy, they don't ignore it, because they can't.
Crimea was Russian originally not Ukrainian. Of course they stole it from somebody else before that.
The Ukraine has a long history with Russia, and when the Soviet Union split up the west agreed to not try to get the Ukraine into NATO, EU or other western organizations. Russia sees the Ukraine as a buffer state and don't want the west on their doorstep.
The west broke all those promises it had given Russia. Naturally they are pissed from feeling ignored. Russia is a bit childish, but it is simple. They just want to feel respected. That is all we got to give them. When they don't feel respected. They start acting like dicks. Sure it is not fair or warranted, but we could totally avoided this if we had been smarter.