Reagan actually compiled a track record demonstrating his conversion. It was not only in the two years leading up to his candidacy, when he made it clear he was positioning for a run.
Trump was supporting several liberal stances and helping the likes of McConnell in 2014 when it was clear he was a sellout to conservatives.
From one year i changed from a hardline atheist who hated Christianity to a Lutheran christian, people can change.
What does trump gain from this ? This is costing him alot of money, he is genuine because he knows how much damage his stance on immigration and Muslims is doing to his brand.