Because he wanted to move to FL? It's probably a basic reason why he moved - Gabby being there is an additional reason, but I'm guessing that like many NYers, he simply wanted to move to FL, where he thought, at least, he wouldn't be completely without family.
I think so too. In fact, it's one reason I'm so interested in "Van Life." Its very nature is ambiguous and if practiced full time, is actually classified in most places as "homelessness." I'm pretty sure that Gabby and BL did not think of themselves as permanently on the road, they knew they had some places they could come back to roost. I think that's true of many Van Lifers - they may want to spend most of the year on the road, but in the winter, they drift south if they can, and park at some family member's house or a friend's. People are constantly allowing Van Life friends to park in their driveway on reddit (especially in big cities).
Near Yosemite, where the park actively limits the number of nights a van can stay, Van Lifers leave the park and there are several known houses with fairly large acreage where they can park (these are the climbers and hikers). There are also several other campgrounds (also with time limitations, but they can be combined in various ways to get a Van Lifer several months of low cost "rent." Many of these will leave the area in the coldest part of the year and go to Baja for a couple of months. Fishing is good, it's warm, food and beer are cheap.
Gabby and BL would have had 3 places in FL to rotate their winter stay if they wished and family allowed it (I believe they would have). And a place in New York, too, for part of the year. I do think this is the basic pattern for Van Lifers - not completely on the road all the year, but trying to avoid permanent living anywhere.