Shocking as it may seem to you, religion and politics have been bonded at the hip in the US for 240 years. To suggest that this is right or wrong is moot. It is what it is.
That left aside, why would Falwell and Dobson openly endorse Donald Trump? For the same reasons so many, more than in any other Republican leadership race, chose him over the other elitist Governors, Senators, Surgeons et al. People are fed up with the corrupt status quo (cronyism,corruption, debt, more war). All the other candidates represent that. They benefit from it. The elite look after themselves at the expense of all the others.
Robert Gore writes: “The mainstream media is filled with vituperative, patronizing, and insulting explanations of what’s behind the Trump phenomenon. It all boils down to revulsion with the self-anointed, incompetent, pretentious, hypocritical, corrupt, prevaricating elite that presumes to rule this country. It is, in a word, inferior to the populace on the other side of the yawning chasm, the ones they have patronized and insulted for decades, and the other side knows it.”
If Dobson, Falwell and others can convince those who believe in them to do what is best, all the more power to them.