Republicans don’t need to vote in the Wisconsin primary election, Trump is the nominee. Their actions to prevent a delay clearly show they want only Democrats to be forced to go congregate in large crowds. The very active voters in the population are mostly in the highest risk group for death in this pandemic. Therefore the Wisconsin Republicans are clearly hoping to kill many Wisconsin Democrats.
The Supreme Court, in an unsigned opinion from which the four liberal justices dissented, reasoned that extending the date by which Wisconsin voters could mail absentee ballots “fundamentally alters the nature of the election.”
Source: Wisconsin: Supreme Court halts absentee ballot deadline extension