This is a pretty good analysis of Trump's popularity.
https://www.vox.com/politics/2024/2/24/24080974/south-carolina-gop-primary-results-2024-trump-haley-trumpism
"Trump’s celebrity charisma alone isn’t enough of an explanation. Otherwise, former California Gov. Arnold Schwarzenegger would bestride the GOP like a colossus. Nor is Trump’s fawning coverage in the conservative media. Fox News has repeatedly tried to turn the Republican base away from Trump and toward figures like DeSantis, only to have to kiss the ring when the voters didn’t follow their lead.
The answer, at least as far as I can tell, is that Trump’s cult is the product of his unique ability to channel the cultural grievances at the heart of the current Republican party.
Again and again, social scientists found that the best predictor of Trump support among Republican voters is the degree to which they feel discomfort with the changing nature of American demographics and social norms. Trump has sold himself as the only person capable of fighting back against the alleged elite conspiracy behind these changes, saying things like “I alone can fix it” and “I am your retribution.” From these building blocks, he has created a full-scale political movement dedicated to reconquering America.
Trump’s appeal isn’t premised on delivering concrete policy goals, nor even “owning the libs” with high-profile stunts. It is about assuaging the sense of fear and resentment at their America being replaced: about achieving victories that assuage the sense of psychological assault created by things like mass immigration, a Black president, shifting gender roles, and a beloved beer brand cutting an ad with a trans influencer. Donald Trump, as a figure, represents the America they know and love. His victories are their victories, his defeats their defeats."