Although previous reply from Bettie is right that, to some extent, Wis Repubs are freaking out over the recent, "safe" state Senate seat they lost badly in a special election, it's even more fundamental for them than that.
I say it's because they're wholly reactive, reactionary bulldogs. Many of them and all their leaders in the legislature and party are pissants of the Trump kind, easily offended and always compelled to take no prisoners.
So, after their pals on the state Supreme Court got Scott Walker and a bunch of "independent" conservative campaign groups off the hook for colluding in an election, the party proceeded to go after the prosecutors (chief among them a special prosecutor who's a Republican, just like Bob Mueller).
And they deleted from long-standing state law the political investigative functions of the state's John Doe closed-door process.
And they wiped out the non-partisan Government Accountability Board that oversaw state elections and replaced it with the bipartisan (not the same thing) Elections Board. Which new office carried over many non-political civil servants from the old. Which pissed off the GOP, even though that's the law. So now the GOP is thinking of just going the whole nine yards and creating a partisan office, in name still a bipartisan office, but only staffed with GOP agreeables.
The GOP targeted the two (among more to come, I'll bet) Elections Board staffers -- despite their civil service protections -- mostly just because the pair actually carried out their assigned duties and assisted prosecutors in handling paperwork and other duties for the Doe probe.
At least one of those two civil servants appears to be a Republican. The party doesn't care. It's Big Brother. It reflexively seeks to destroy all perceived opposition in the worst possible way, to make examples in every case, no matter how small the slight, perceived or real. Authoritarians of the worst sort.