A lot of those big vans are top heavy when fully loaded
There has been many accidents with those large vans. They're popular with church groups and the like because they can carry a lot of people, but they're a handful to drive when loaded. I drove one full of people from Onizuka to Vandenberg back in 1988. Despite almost 100,000 miles of experience in vans, that was a challenging drive. I'd never driven one that unstable before.