If not what can be the reason?

Yes.

The first is to describe why something HAD TO happen. The second is to describe why something DID happen.Just "the reason" is what it is, and it can be used in three different ways. You used two of...

Reason is the ability of comprehending, inferring, or thinking, and the use of logic. It is otherwise known as the intellect.

i cant stay on one thought with out having two things going on in my head

a famine