I'm beginning to think they just forgot to lower the gear on the first landing attempt, so they attempted a belly landing.
If they forgot to lower the gear they would not attempt a belly landing. They would go around -- which is what they did. As other posters have pointed out, if the go around was initiated too late and/or the gear retracted too soon (if it actually was down prior to the go around) then that could account for the cowlings scraping the runway.
I have read that 3500 feet at 5 miles is way out of sorts for the approach, so they needed to get down pretty fast to make the runway.
A few questions present themselves.
When did they realize the gear was not down?
Did they tell ATC they had gear problems? (So far, it seems not)
How long does it take for the gear to cycle to down and locked?
What attempts were made to get the gear to go down, prior to the go around? (Assuming it was a gear problem and not a pilot problem)
Why does ATC say "belly landing"?
Do the comms we have so far indicate that ATC was dubious about this approach?
I think the full comms transcript and the CVR and DFDR readouts are going to confirm the bizarre aspect of this crash.
Assuming we are ever allowed access to them.