W.European defence has been based on the US for 82 years and it's hard for European leaders to imagine a life after that.
"Well there is widespread acknowledgement that Trump getting elected in 2024 could lead to the US cutting all aid to Ukraine, and the Europeans view that as a catastrophe—there does seem to be no real planning to deal with such a contingency. They know it will be a disaster, but its almost too large for European states to comprehend at this point." https://phillipspobrien.substack.com/p/weekend-update-48-stalemate-or-not