Illinois went ahead with their primary, which was really dumb, but it wasn't the same as this. Because the Illinois primary occurred before things got bad enough for everyone to understand and before there was a shelter in place order, there wasn't a big surge in absentee requests that the state failed to fulfill on time. There wasn't an equivalent situation here with ballot access, and there weren't really important partisan elections like the WI SC seat. It was local referendums and intraparty primary choices.
In parallel to this, Governor Evers arguably waited too long to try to postpone the election, but he did call a special session of the legislature over the weekend. This session was immediately ended by the GOP majority.
Across the country right now, one party is trying to make mail in voting widespread ahead of the November election to address this issue while the other is blocking it. It's a public health issue, and not really a "both sides" thing here. A few politicians of one particular party have been very explicit as to why they oppose this: they believe it'll increase turnout which will be better for their political opponents. Recent election trends show that may not even be true, but that's their clearly stated reason.