Their filed route was 962 miles. I didn’t pull that 1000 number out of my rear. And the size of the people is only part of the equation. Their luggage counts too, and some people pack the kitchen sink.

Assuming and average weight of 180lbs over 10 people and 50 lbs of baggage per (one carry on and one checked) and you’re quickly in the 2300 lbs of payload plus probably another 2200lbs of fuel or so. That puts you within 500lbs of MTOW right there.

W/B issues are well within the realm of possibility.