There's a vague possibility that they had a flap asymmetry (which locks the flaps in present position) - and pressed on.
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However the more I read about passenger and witness descriptions of their perceived sequence of events, the clearer it is that the nosewheel was driven in and that a destructive PIO called "porpoising" began. Porpoising can become a divergent phugoid in a jet that's landed far too fast for its weight (and with insufficient drag flap).
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What's Porpoising?
After the nosewheel oleo rebounds upwards and the aircraft "bounces" (courtesy of the MLG oleos decompressing a short time later), the neophyte pilot's natural tendency is to instantly lower the nose and again "spot the deck" (i.e. try to force the airplane onto the ground). It's completely opposite to a normal flare and hold-off process. The inevitable result is another nosewheel first strike (and rebound). The PIO is underway......
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This apparently happened three times and on the third occasion the nosewheel oleo snapped off (thereafter no hydraulics, no nosewheel steering, no directional control via rudder, no reverse and MLG braking only from the brake accumulator - about five applications before it's empty).
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Complicating matters in turboprops and piston-engined airplanes is the instant power response that's available (i.e. pilots can easily get "out of sync" by adding power in the bounce [i.e. on the rebound]). That added power cycling tends to "eat up" runway remaining. However to achieve the same porpoising effect in a jet, you just have to be "hot" (and high) over the threshold, have little or no flap (i.e. drag to kill off your float speed), try to force the airplane onto the ground (resulting in a tricycle landing or even worse, striking nosewheel first).
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You might recall that I once told you about this being done to me by a gent called XXXXXX in an SP2H Neptune at XXXXXX. He looked up at night to locate and dump the jets, (whose throttles were in the overhead console), and inadvertently let the nose drop whilst in the landing flare. Wildest ride I ever sat through (as a young copilot). Coincidentally he had the worst stutter you'd ever imagine acceptable in a pilot. Seems fitting somehow that he could also create the most memorable porpoising ride of my flying career.
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Back to porpoising. Adding to these self-wrought woes is the fact that any power "adds" (or throttle manipulation) will inhibit spoiler extension and add to the overrun likelihood. Even without throttle jockeying, you still need the MLG squat switches to be depressed long enough for the spoiler panels to pop up (and then of course, the oleos to remain depressed). During porpoising that just won't happen so, lacking that spoiler effect, the wing just keeps "flying". It's a PIO cycle that's destined to end up destructive and/or off the end, particularly if you're hot and have landed much too far in. We can expect to see many more of these types of "mishandling, confused and fixated" accidents the world over - as pilot experience levels drop (and the new MPL licencees move up in the airline world).
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I have a fairly high degree of confidence in this theory having been the underlying cause for Flight GA200's fate once they'd touched down. But why they allowed it to get hot on finals? I'm sticking my neck out by saying that the RH seater just neglected to select flap (or only took 15 degrees and then totally forgot about the flap lever because of the distraction of a wind-shear/microburst and overshoot trend). If they flew through a sharp gust or thermal and picked up a temporary tailwind and just lowered the nose to correct the overshoot trend? Well that would just indicate a fairly inept handling of a common everyday problem. Unless there was some other complication, I'd tend to put it down to an inability to cope with the environmentals - and the inexperience of the RH seater. I believe the captain was actually quite experienced, but probably let it all go too far. Porpoising is a PIO - and by definition it can be a self-sustaining destructive process. And fixation (leading to task saturation) is by far the most common cause of mishandling accidents during the landing evolution.
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For some examples of porpoising, try
this link