Question

Why do you think that some asteroids tumble end over end through space while other asteroids rotate around their axis?

Answer 1

Imagine a lonely asteroid there in space, untouched, not rotating, just still. Then another asteroid passes by and comes into contact with that first asteroid. Upon collision, based on the conservation of elastic momentum, the asteroid that was once still moves; it may even spin if the incoming asteroid hit it at its side. Now asteroids have three angles or rotation (three dimensions): θ (theta - to the x-axis), φ (phi - to the y-axis), and let's say ψ (psi - to the z-axis). So these asteroids wobble through space, spinning like crazy.

I may have gone too in depth. Sorry, lol.
I hope this helped!