Because Geraldo is an opportunist.
He wasn’t always pro-Trump, only when he realized his mileage on Fox would go farther if he was.
Acrually Geraldo was fairly pro-Trump all along. While he didn’t say so directly he hinted he would vote for him over Hillary. He said he disagreed on immigration but other than that he thought Trump would be a good president, and the characterizations of Trump as a buffoon were nonsense. He’s known Trump a long time and was on Celebrety Apprentice.