I think the Laundries knew it was rocky. Unless RD is lying, Gabby occasionally left for her house for a night or two, when they were fighting. No matter how many engagements a couple announces, parents who live with said couple know a *lot* about their relationship. The picture we saw yesterday:
Sleuths think Gabby Petito may be holding GUN in photo as cops hunt fiancé
shows a single bed. Did Gabby have her own room? Or...actually no room at all? Since she had lived with them for 2 years, was this last move (not too long before the Van Life started - and they left from NY)...was this move an attempt to push Gabby out? It's not easy to evict someone, whether they pay rent or not, from their residence, even if their legal residence is somewhere else. Maybe the Laundries were tired of this "engaged couple" living with them? It sure looks like a room occupied by a lone male (as does his other earlier room shown so extensively on Insta, which he apparently occupied until rather recently - I'd have to check the dates).
Anyway, the Laundries had been in this place maybe 3 months, and I see no feminine touches or a comfortable place in Brian's room for Gabby.
That's a big red flag that the parents may not have wanted the couple living indefinitely in their house. Like all couples, surely they had their problems and fought sometimes, but as a parent of adult children, I simply did not want that couple living in my own house. They needed to grow up and go see if they could work it out together (not on the road, though!)
But it looks like the parents provided
Brian with a cozy little room. If my theory is true, then Brian's desire to live the Van Life is connected to wanting to be with Gabby in face of his parents saying, "Look, we want a retirement lifestyle, we want our house to ourselves, you can stay if you pay some rent, but Gabby needs to find her own place." Gabby takes the money she's saved up for a potential apartment and invests it in Brian's idea of Van Life.
But I think the Laundries may have known about the issues (just like the high school friends did), and may not have liked Gabby that well. Parents have this habit of blaming their kids' partner instead of their kid. Here on this WS thread, there have been several posters writing about how much they secretly despise their kid's partner, and are relieved/delighted when there's a break up (or even a demise). I doubt that the Laundries absolutely hated Gabby, but perhaps they felt she was drawing Brian out of his comfort zone. They knew, in a way. that she did not, that he could be very difficult and they thought he was best off not having a serious relationship...maybe
So Brian goes home to FL, but then realizes he wants "his" van back. He thinks of it as his regardless of the registration and people here have also said, well he has "sweat equity" in it; they were engaged, it's obvious it was "community property," etc. So he flies to get it, Gabby pleads with him to at least try again, until Yellowstone, she'll be good, won't be so "OCD" and off they go, patching things up as they have done so many times before. I don't think Brian was capable of breaking up with her (for many reasons), but I don't think Gabby was capable of managing him on the road, the way his parents would have tried to do. And Gabby didn't want to break up.