You are saying essentially that Ukraine should have been part of NATO. After all the reason for NATO is that any one country, including Ukraine, is not sufficiently powerful (apart from the U.S. perhaps the UK) to repel an attack from Russia.

Yes, Ukraine possibly should have been in NATO. However there were many in the U.S. against the expansion of that responsibility. Trump offered doubt that we would abide by the agreements that we had signed up for.