Sorry if :late: I'm still catching up on the thread so maybe this has been said. The answers are in their twitters if you care enough to dig through.
Oney moved to LA, maybe at Arin's sugestion. Before the official move, Oney had visited Grumpspace...appeared in a video or two and some streams? I can't remember exact timelines but Brian was still appearing on camera and running social media stuff. Perhaps because Oney was inbetween jobs at the time and maybe figuring out how to avoid having to move back to Ireland or something. I remember him posting something about thanking Arin for helping him out with Visa stuff. Letting him re-start up his, then, casual let's play channel by allowing him to record there. Oney brought with him his friends Ding Dong and Julian. Ross even had Oney Co-Host a new series for the channel, Doodle Doods...which I guess officially made Oney a grump in a way? Things were chugging along, Oney presumably earned enough to move out of Arin's and get his own place.
Then the Dream Daddy stuff happened, which has already been covered. Ding Dong and Julian openly mentioning their distaste for it, Brian and Suzy clapping back at them, yadda yadda. And eventually Oney and friends stopped recording at the Grumpspace. But the Oney guys kept publicly insisting this only happened because of scheduling problems. I think maybe weeks or months down the line Oney made a vague tweet about knowing who your real friends are or something to that effect. And people were concluding he was talking about a falling out with Arin.
I dunno if this has been mentioned yet either, but it's sort of tangentially related. There was a very brief period of time were Markiplier was in a bad place (a break up I think?) or between moving houses, and the Grumps let him stay and record there. Long after he got his stuff back together and moved out, Markiplier eventually employed his editors Matt and Ryan and then had a falling out with them. Matt and Ryan went off and became Game Grumps' current editors and started their own LP channel, Super Mega. Markiplier made a sort of apology/confession post on Facebook that mentions how he was hurt about it since he thought Game Grumps were his friends. Super Mega also got really close with OneyPlays. But now have seem to have distanced themselves from Oney as well. At the behest of boss Arin? Or on their own...that's still under speculation.