Answer:
Warsaw Pact members has not been volunteer members of pact equal to Soviet Union. They was kind of dependent colonies. If any of them wanted to exit, SU and other members was sending their armies to “return order”. Your know: Berlin 1952, Budapest 1956, Prague 1968.
So, when finally SU broke into parts and Warsaw Pact become irrelevant and untied, we all felt free and want to remain in such state.
But Russia is the last colonial empire, it was obvious to most of us, that one day, they will start rebuilding their empire. So we wanted to be part of real defensive pact. The only and one in Europe, powerful enough to save any and all of us from Russia is NATO. So we asked to join and after come preparations become members.
Current war in Ukraine clearly shows they we was right!