I previously thought the same, with Europe and Russia doing lots of trade e.g. Germany buying lots of gas from Russia, and many western companies being present in Russia. It seems obviously true.
But Russia still started a war anyway, so I guess it's not actually true.
Putin or Trump are totally isolated from economical and political consequences so they have no problem severing ties. If there are genuine co-dependencies, including for the leaders, they it's much harder to break peace.
I imagine the ideological aspect is the deeper motivation but it only matters with the right circumstances.
Putin and Trump sits in the opposite side of the political spectrum, so as the country they lead, and yet they still managed to archive something similar.
It's not that hard to manage the country to a point where nothing in the country, even law, can hurt it's leader anymore. Sometime a bit of time and patient is all it takes.
So it's not actually caring about the war and dead people (if we did, we'd do something about what israel is doing in gaza), but "us vs them", and russia is "them" while US was traditionally "us", until daddy Trump came along.
Someone probably told the EU politicians that russia will cave after a month or two of sanctions, there will be some kind of a "revolution" there, someone "pro EU" will be set there, and gas would be even cheaper.... A similar scenario was probably given to Trump for iran (just bomb the government, they'll cave, and you can set up a new pro-US leader there again).