Normies operate entirely by aesthetics and vague impressions of social norms. They'll accept Trump being removed as long as there's some (false) consensus that he's a criminal, and ignore that Colorado became a one-party state with that excuse. My take is, Republicans choosing to pull themselves out in direct response to Democrats is a play meant to put the responsibility for Colorado being one-party back in the hands of Dems, in hopes that it will put the centrists in a difficult position by highlighting how it was an aggressive capture, not bureaucracy operating as expected.

I don't know that it matters insofar that Colorado was going to vote Dem anyways, but that also means they don't have much to lose by trying. However, it's definitely doomed to fail if somebody breaks ranks.