the reason why we have this mess is because the states get to make up whatever rules they want around voting so long as they never officially block you from voting. doing so would force the federal government to step in, so the red & purple states are careful not to poke that bear and instead focus their voter suppression efforts on the aspects of voting that previous court cases had decided that federal government has no say: like registration.

biden won because several purple states managed to make registration & voting easier (eg most of the battleground states) and they’ve all since then repealed that easier access.