He probably wanted to take advantage of the LGBT community, and he probably only had those profiles for the wrong reasons.
He probably went to Pulse because he had the idea for a while, and wanted to know exactly how he was going to do what he did.
I can't believe someone would do something so awful
Edit: Maybe he was gay?? That wouldn't really make sense though. Unless he thought it was a sin so he wanted to kill himself and other gay people with him because he was mad. He apparently was a part of that hate group, I can only imagine the awful things they told him about the gay community.