Snowden has always considered himself a patriot.
It was his love for America that motivated him to expose the illegal and unconstitutional activity going on inside the intel community.
He sought asylum in other countries (Russia finally granted this) just to avoid retaliation from Clowns and black hats - he surely would have been 187’ed for this release, and he knew it. The only way to get the word out and make the American public see the evidence first hand was to release it and be around long enough to bring awareness to what has been happening.
So, my bet is that he’s been working for America as a patriot. The right man came along (DJT) and he’s been able to start working his way back in, providing evidence and data, and re-proving his loyalty to the USA, the country he holds dear in his heart.
I don’t purport to know what’s in another man’s heart - that’s Jesus’ job. But I offer this more as a hypothesis based on what he has said. Of course, it could all be a ruse to get sensitive data into the hands of our adversaries, biut I don’t think so.