That is a loaded question.  Why would you think someone was responsible for this explosion?

Where is the evidence for it?  Not every fallen tree has fallen because someone chopped it down.

Nobody knows for sure what happened during times less than 380,000 after the Big Bang.  There is an ongoing study of gravitational waves that might shed a light on this period as well.

A better question is how the Big Bang happened?

What happens when a Black Hole collapses on itself and explodes?