Back wheels spinning in water create weak driving force forward.

Front wheels can turn and provide rudimentary front rudder effect wrt force from rear wheels pushing forward.

If 4xwheel drive was engaged the front wheels wouls also be driven and provide a "clawing forwards" directional force.

It's not the ideal boat, but it floats and works up to a point (as seen).

With the engine weight forward it's entirely possible the front wheels were occassionally touching down when over the pan of the crossing.

When the vehichle went to the left of the crossing it's unlikely the front wheels had any contact as the crossing (unflooded) is typically higher than the river bed on either side.

Looks to me like mostly momentum and current carried him to a spot where his front tires touched bottom at which point he was able to spin around. He was pretty adrift until he hit that spot.