Stupidity
specifically - failure to land perfectly functioning parachutes correctly. The transition time from intermediate to advanced seems to take out a lot of jumpers.
There are high performance canopies on the market that are under 100 square feet in size, that are jumped by 180 lb jumpers, and fly with max forward speeds of something like 30-40 mph. It takes some skill to flare these things on landing and convert speed to lift at the end. Misjudge the performance curve and you're toast.
I don't fly stuff like that but its considered "cool" to "swoop" your landings (dive to gain speed, pull out and convert speed to lift for a long "turf surf" a foot or two above the ground). Problem is, some people don't initiate the recovery from dive soon enough and pound in.
You don't have to fly stuff this zoomy - only if you wanna be "cool". I'm not cool.
"One of the main causes of the fall of the Roman Empire was that,
lacking zero, they had no way to indicate successful termination
of their C programs."
-- Robert Firth