Some good discussion in the nested comments:
Imgur video link
From what I can tell:
1. These were the RC units, not final production
2. No recovery points to attach to (guessing the finals will have this)
3. Wrong tires for the conditions
4. Tires weren't deflated
5. Electric motor provides instant power, making it difficult to ease into a roll (I'd imagine they'll have a creep/crawl mode in a software update)
6. No traction aids (traction tracks etc.)
7. More difficult to do gear-shift rocking of forward & reverse (gear shift is a touchscreen on the inside rooftop of the windshield)
8. Really have with a low center-of-gravity (6,000 to just below 7,000 pounds, depending on how it's configured, plus the weight of the human bodies inside)
The officially listed max ground clearance in Extract Mode is 17.44", which is pretty cool for getting un-stuck in deep conditions, but this was snow & ice, with no chains on the tires or anything.