Nobody has proposed that everything "just accidentally happened". That's just a strawman. But still, saying that "everything is an accident" or "not everything is an accident" would not constitute a scientific theory, because it doesn't make predictions, it isn't falsifiable, and it doesn't unite disparate phenomena into a coherent framework. It's just philosophy.
Out of curiosity, how do you define philosophy? This is one of those words that people seem to have a lot of different personal definitions for (as well as the several that exist in the dictionary). Just curious.