Either lack of critical thinking or driven by greed.
You get the top to vote for you by ensuring they keep and/or increase their riches. That’s done by immediate things like tax cuts, or other long term strategies like cutting environmental protections and reducing the role of gov’t, allowing businesses to rape the planet and abuse their workforce as hard as possible to increase profits.
As for the rest of his supporters, the “MAGA” crowd, they’re kept in line by keeping them stupid, allowing you to more easily feed them propaganda and influence their emotions to fit your needs. Religion teaches them to be subservient from an early age and take a back seat to a higher power, whether that be god or the charismatic talking head at the alter or on tv, all the while leeching as much money from them as possible without leaving them totally destitute. This helps explain why conservatives/religious turds continue to attack early education (less chance of them learning to think critically and question things), school lunch programs (hinder brain development), libraries (access to other ideas/beliefs), sex education and abortions (keeping those accidental pregnancies from being stopped, thereby ensuring the already uneducated and poor families continue to have kids they cannot support financially and give a good education to). It’s all very sinister when you look at the whole picture. It’s why I detest religion, not so much the concept and practicing of religion, but how evil men have turned it into a weapon, and exploiting the very people they pretend to care about. A lot of the evil they push is all done under the guise of religious beliefs/freedoms.