One of the things I've read about why things are the way they are is a comparison to probabilities, the thought is that similar to how there is one and only one way to roll a bunch of dice and have them come up all ones, there would be one and only one way for there to be "nothing" in the universe given the existence of any energy because of how many different ways energy can exist it's much more probable that you get a jumbled pile of all kinds of different things.
Now as for the question of "where did all this energy come from" you have to realize that even the vacuum of space contains energy of some level and the 'visible universe ' that is all of the matter that interacts with electromagnetic fields only accounts for a tiny fraction of the total energy we can detect so it's likely that the energies that make up our matter and universe came from "somewhere else" ... but then where did that energy come from and then it's turtles all the way down