Originally Posted by
B2N2
It is not a stall. You can see the aircraft gaining altitude relative to the high wing twin. In a stall it would lose altitude. The article linked to has a second part (addendum) that describes what happens: the driver ran out of forward stick and trim due to the group of skydivers hanging on and blocking the tailplane.
Anyway, we do not know what happened to the aircraft involved in the accident in Switzerland. Time and a thorough investigation will tell us.