Alien: Covenant.. Why

So, I finally watched Alien Covenant last night and I enjoyed it. Sure, everything was predictable BUT that didn't take away from the fact that it was a good movie. A movie about David.

What I didn't understand is why did David Kill the Creators? He has a God Complex and he wanted to create life since he thinks Humans are a dying race.. I don't understand why he wanted to kill the Creators if the Creators wanted to kill humans too.