We’d had a smaller van before but once we knew we were going to be three humans, it wasn’t big enough.
We also wanted to be able to drive around the world in something that (hopefully) wouldn’t shake itself apart at the first washboard road and that could get us access to off road, out of the way, places that a normal van wouldn’t be able to.
Lastly, this is a long term trip, so we wanted sufficient space to be comfortable even in bad weather, with the amenities that would mean it doesn’t feel like camping.