Are both sentences OK?
It happened what it was supposed to be.
It worked out what it was supposed to be.

Question

Answer

Better way:
It happened the way it was supposed to.
It worked out the way it was meant to.
It worked out the way it was supposed to.

Answer

It would be better to use either:

It happened the way it was supposed to.
OR
It worked out the way it was supposed to.

You could also use "how" instead of "the way". But both are better than "what" in this case.