Lol did I say any thing about going faster ?
Longer crank means your foot needs to move a longer distance.
Meaning on a run up while your traveling at the same speed you legs need to move further and faster.
When you do the last two pedal rotations you then need to accelerate your leg speed for the final kick to propel forwards and upwards. That takes alot more strength.
Your argument seems to assume that the only method of proposition in trials comes from your legs.
When you jump your using alot more muscle groups.
Yes I agree longer gives you more leverage. Might help on a short run up on a steep slope to start moving.
But in trials you want to be accelerating more and more the closer you get to the object.
No point in slowing down
You also can start closer and still get the same rotations in with shorter cranks.
There is a simalar argument in track cycling