If he had landed on that incline in soggy soil and then tried to lift off, he set himself up for a classic rollover. If he gave it power to get out of the muck instead of setting back down, it'll go sideways everytime.
It doesn't look like he tried to land - no dimples in the dirt where the wheels would have dug in - and besides, there is no reason to land there (except if the aircraft decides to. :-P ).