Question

why is earth's axis tilted

Answer 1

Earth's axis is tilted due to energetic collisions between the ‘planetessimals’ which eventually coalesced to form the planets, knocking them off the perpendicular orientation they would naturally have.

Answer 2

Earth is tilted on an axis of 23.5° from the plane around the sun.
The main reason why earth's axis is tilt and what happens to it is seasons. The seasons r caused due to the tilted axis of earth.
Frnd do u know that it is also assumed that the ice age was also due to tilted axis of earth.
Hope this helps....