What I remember from the original Canny video was that the vehicle in question had made it through the river. IIRC the air intake point on the fenders of each vehicle shown were often dipping below the water line. Ineos has stated that the RAI components are not watertight so I thought everything looked sketchy and evidenced bad judgement but I don't know anything about water crossings. After the crossing the party then camped for the night a very short distance further down the road. In the morning when the engine was started the vehicle made a racket, died, and leaked oil.
Here is my immediate thought at the time:
Overnight the water ingested during the day before - highly aerated and in small amounts at the time of the crossing - settled or pooled into the lowest portions of the intake system. When the vehicle was started next morning there was just enough air volume in the intercooler ahead of the where the water collected to fire up the engine for a brief moment - possibly just a single revolution or two - and then the water "plug" was stuffed into a couple of cylinders en masse resulting in an hydrolocked motor.
Or it was a sham like
@Zimm said.