The EU can't let Russia "win" as it would set a precedent. If the US withdraws their support, the EU will have no choice but to ramp up theirs, meaning funneling money to the military complex. Double or triple that if Trump goes through with his NATO defunding/withdrawl threats. This could easily destabilize the EU economy, cause internal friction, provide fertile ground for nationalism and, ultimately, lead to the fracture of the EU. Now recall Trump's cordial alignment with Putin, which will undoubtedly encourage this sort of development, and it all starts to look outright scary.