The expansion of space itself is not comparable to the speed of light, but yes, I would say it's probable that it would have caused particles (or whatever there was at that time) to spread out faster than light, thus disconnecting them causally and preventing gravitational interaction. As for the why, answering that would involve answering why the Big Bang happened, which given our current understanding would veer into metaphysics. As far as we can tell, it's just what the universe does.