Surely the Wisconsin legislature, if it desired to direct these efforts, could muster a plurality of the state legislature to override or overrule the Governor, could they not? If it's truly a case of gubernatorial overreach, it's not like they don't have a wide variety of options at their disposal. I'm hardly a legal scholar, but I have yet to hear of a state that hasn't been able to override a governor's decision making process if they really felt the need.
I'd buy Wisconsin Supreme Court's justification if we weren't talking about a fucking pandemic, but here we are.