Isn’t this the case always The kinetic energy is conserved.
No, it isn't.
However it is correct that in elastic collision the total kinetic energy before collision is equal to kinetic energy after collision .
The kinetic energy isn't conserved during collision that is during collision the two bodies remain in contact. Depending on the situation a part of whole of K.E is converted to elastic potential energy of bodies.
Take the example of two similar bodies approaching each other with same magnitude of velocity and colliding head on . During brief period of contact whole of K.E is converted into potential energy