The rocker insisted on a hiatus from the group at the beginning of 2015 and as a result he was kicked out - and now he's opening up about his bizarre reasons for walking away.
In a new interview, Tom admits he wanted to spend more time investigating UFOs and the aliens driving them.
He told Mic, "Dealing with something that's a national security issue, and you're being gifted with the opportunity to communicate something you've been passionate about your whole life - something that has the opportunity to change the world over time - being a small part of that is enormously important for my life path.
"But I can't do everything. I can't tour nine months out of the year with enough time to do the enormity of what I'm setting out to do."
And he's deadly serious about his UFO passions - he recently released the book Sekret MAChines, which delves into accounts of UFO sightings and alien abductions.
His old bandmates have moved on without DeLonge, recruiting Alkaline Trio star Matt Skiba to replace him.