You forget something.  Paxton Lynch didn't get a whole lot of playing time last year.  Since he didn't play a lot in Kubiak's offense, it's unrealistic to expect him to be familiar enough with Mike McCoy's offense to earn the QB job this year.  Trevor has proved that he can adapt.  And with the Broncos' improved O-line play this year and(it's hoped) a better running game, Trevor has a chance to improve on last year's stats.