They might have lived in shallow marshes like hippo’s right?
Looking at the roughly scale picture in post 33, they have about the same amount of footprint on the ground as the 737 jet, plus the one more foot. Also have roughly the same clearance. A jet runway is very thick concrete to support the weight. Run a jet into a marshy area and the wheels sink and the belly rests on the surface, then suction holds it there.
I would think they lived on dry hard ground with no heavy rains to make mud, or deep water where they could wade and float a bit.