Ukraine, like most of Europe, uses electric trains almost exclusively. Ukraine uses trains to transport weapons and ammunition from Poland across the country, and troops within the country.
Taking out the electrical distribution system means severely hampering Ukraine's military logistics.
I'm sure this does harden the resolve of the Ukrainian defenders! I don't know if a majority of European citizens feel the same. European leaders are something else.
It certainly hardens my desire for Russia, Ukraine and the US to really negotiate in earnest for peace so this horrible war ends.