Republicans have discovered how to "hack" democracy. I think it's pretty clear both sides have engaged in some pretty egregious gerrymandering in different parts of the country, but only Republicans have become so hostile to allowing people to actually vote. And while both parties' positions on voter laws may be due to self-interest (marginal voters are more likely to vote Democratic, so barriers to voting are more likely to negatively affect Democrats) it doesn't really matter - the Republican position of things like shortening early voting, closing tons of polling places in spots like university towns, forcing a vote during a pandemic is bad for democracy.
The Supreme Court ruled against the plaintiffs (not surprisingly, 5-4 I might add), but in the grounds that the federal courts didn't have the power to intervene in cases of political gerrymandering, but no one really debated that the Wisconsin maps heavily favored Republicans over what a more normal, compact map would produce.
Wisconsin is just corrupt. You wouldn't believe the geometric gymnastics they jump through to try to get districts that will always vote liberal or conservative. Districting maps look like something from mc escher.