Obviously, Trump's willingness to embrace lies makes things worse. He is an elderly conspiratorial Fox News viewer and motivates that demographic.
There are a few differences that made 2020 a perfect storm in terms of bullshit allegations.
First, it was pretty close. In 2020, the difference between Trump and Biden in Arizona, Georgia and Wisconsin was under 0.64%. Had it gone the other way, he'd still be President. In 2012, the difference between Obama and Romney in the tipping point state of Colorado was 5.37% (it was also 5.39% in Pennsylvania. 5.51% in New Hampshire and 5.81% in Iowa.)
Due to Covid, there were changes in election administration and oversight, which meant skeptics had something new to point to. It was also the most high turnout election in a century, and some Trump allies had been priming people to expect some kind of fraud. Many of the people primed would be unfamiliar with basics of election administration, and make honest mistakes out of ignorance. Two months before the election, I wrote the implications of the red mirage, as in-person Republican votes might be counted before Democratic-leaning absentee ballots, resulting in initial numbers that favor Republicans.
https://community.cbr.com/showthread...=1#post5126024
Trump isn't necessarily more right-wing than Romney. He was a Democrat up until 2009, and took some moderate positions in the 2016 primary.
https://www.csmonitor.com/USA/Politi...what-you-think
https://www.vox.com/policy-and-polit...ate-republican
What made him appealing to right-wingers was affect rather than substance. One of the claims I've heard from his supporters is that Republicans who fight win. The way they see it the likes of McCain didn't fight hard enough, because they weren't willing to go after Jeremiah Wright, or Obama's college grades, or whatever. Trump would invite Bill Clinton's accusers to presidential debates, and suggest Joe Biden's top priority as Vice President was helping Hunter Biden's patrons. The asshole conservatives feel validated by Trump's win even if that's more due to timing than anything else. Ford, Papa Bush and McCain lost because parties have a tough time keeping the White House for more than two terms (Bush's 1988 win was historically unusual.) Dole, and Romney lost because parties tend not to get kicked out of the White House after one term (Trump's 2020 loss is the second time this has happened since 1900.)