• The cosmological constant and Hubble constant are related, but not the same thing (I’m guessing that’s what you meant). Einstein felt there had to be something preventing the universe from collapsing. When he learned that the universe was expanding, he realized that it could just be momentum preventing the collapse, so lambda was a “mistake”.

        It was possible that the universe could be expanding, but with no dark energy. Then it would have a Hubble constant but no lambda