I think what actually happened is that Republicans figured that 1) Democrat legislatures would either be too scared to try this unilaterally like Republicans did, or otherwise get overturned by a hostile SCOTUS, or 2) not have enough time before the midterms to make these changes. They definitely didn't count on multiple states putting up ballot initiatives successfully. SCOTUS could still try some shenanigans, but it would be nearly impossible to justify federally blocking state-level ballot initiatives around administering elections (and Trump has already started pushing federal control, since the midterms clearly aren't setting up to go the way they want).
My real fear is that this entire exercise has been a distraction, and they're planning something else to overcome the midterms.