For over a decade, the refrain has been the same by... pretty much everyone... that the NFL was a passing league. The reason that was believed is because the data showed it. Good passing offenses were more efficient, more explosive and won.
The NFL became a “quarterback, head coach and offensive play caller” driven league. The fact that the passing attacks were seen as more entertaining to the general football viewer (not the hardcore fans) led to the NFL making more rules to make the game more pass-friendly.
The Cleveland Browns saw those trends and have invested in Deshaun Watson and those involved in the passing game.