"Even though Miley and Liam were separated for a while before she was photographed making out on the yacht with Kaitlynn, once Liam saw those photos he decided it was time to file for divorce," a source said. "That was it for him, seeing those photos and then all the Soho House stories thereafter."
Before the pap pics surfaced, Liam's friends and family thought he and Miley would get back together, and a source had told E! that "Their families have urged them to take some time to breathe before they make any final decisions." But seeing the photos ended up being the moment Liam realized that he "can't do this anymore."
That said, Miley did *not* cheat on Liam—a fact she made extremely clear during a lengthy Twitter rant last week. “I can admit to a lot of things but I refuse to admit that my marriage ended because of cheating," she wrote. "Liam and I have been together for a decade. I’ve said it before & it remains true, I love Liam and always will.”
Liam is currently in Australia while Miley remains L.A.-based, and apparently there "are intermediaries who are handling most everything" in what will be a "very amicable" divorce. "He's sad but he's honestly fine overall," the source says. "He wants to just get this done."