Climbing is mostly about a high sustainable power to weight ratio. At 235 lbs an unusually fit rider might be able to pull that weight up a short hill with the fast group. Like putting a heavier, more powerful engine in a car. But soon that big engine will burn up most of the gas and will have to reduce speed to make it to the top. Same thing with a heavy rider.
As for "a fast hybrid" vs an average road bike for climbing, I give the road bike an advantage here, even when air resistance isn't as important. The right tire on a hybrid can bring rolling resistance down close to a road bike, But the road bike is likely lighter and has less air resistance even at reduced speeds.