I didn't realize that Missouri has a Medicaid Expansion ballot coming up on 4 August. Interestingly, that's the date of the primaries for both parties. Turnout will likely be a lot lower than it would be if it were held in November on the date of the general election. Missouri will vote for Trump, and most of the Trump voters will vote against Medicaid expansion. So you might expect that, if you wanted to win, you'd schedule the ballot for November.
However, it's not just Trump who's up for re-election in November- the Republican Governor of Missouri is too. And Missouri does sometimes elect Democrat governors. I wonder if the Governor is happy for it to have passed already and be less of a live issue in his own re-election race.