Here's my general summary of why this is an issue: the US has been denying people the right to vote since day 1. You had to own land to vote in 1788. Half the country seceded and started a civil war that killed more of our citizens than any war since, over the right to own people. The 15th amendment was passed in 1870 to make it so you can't deny Black people the right to vote, but places made it happen anyway. They made it so you had to pass a "literacy test" with intentionally ambiguous instructions, or pay a poll tax, or one of your grandparents had to have the ability to vote (afaik, the origin of the phrase "grandfathered in").
These were all legal until the 1960s. Lots of people here have parents who were alive before legislation was passed to end Jim Crow. Without that, the racists that be turned to the War on Drugs, because lots of places take away your right to vote if you've been convicted of a felony. They started passing voter ID laws and closing down DMVs in areas with lots of black people and reducing their hours. A politician in Wisconsin bragged after the 2016 election that these laws here threw the state to Trump. They've also started banning giving food and water to people in line to vote and throwing out mail-in votes that show up after election day.
This isn't about election security and it never has been; voter fraud has never changed an election in the country's history. The real election fraud is in suppressing people's votes and fucking with voting machines (2004) and having allies in positions of power to throw the election your way (2000). There's more than that too, but it's a tangent.