I think it’s partly his ‘strong man’ persona, but also that he was one of the only candidates hitting on all the things they needed to hear. We need to do more for our rural communities. Help the farmers! Help the coal miners! Keep oil production flowing! He touched on the lifeblood on these rural towns, which is something other conservative politicians weren’t doing as much. That let his message spread wider organically, from people who were quite literally willing to devote their life to him. He ‘stuck to his guns’ (on the issues they cared about anyway) which is what let them ignore the other things he said and did. There was also one of the largest state-sponsored propaganda campaigns in Internet history backing his election. In many or most small towns it became an Us vs. Them (Trump being the Us) and if you know how small towns work then you know it’s “When in Rome…” creating a massive echo chamber across conservative America. When the mob is rallying for something, you stay quiet or face the consequences. Many didn’t stay quiet and became outspoken, which furthered the division.