Thanks to the magic of the internet, we can experience the highs and lows of failing a snowy hill climb on a KTM 525 without even putting our boots on:

https://atvconnection.com/articles/atv-video-ktm-525-snow-crash-ballet/

 

It's hard enough getting up a snow covered hill with a 4wd machine....

 

If you sit on the back of the seat during a hill climb you shouldn't be surprised if it flips over.

 

One Grizzly 660 I had the 4wd wasn't working. I tried to climb a hill that wasn't that steep(just mud, no snow) and it just wouldn't make it. I got about halfway and it just kept spinning and stalled out, had to roll back down. But yeah, it appears he could have been leaning much farther forward.

 

X3 on moving your weight forward on a hill climb. You see sport quad riders tend to shift back more than 4x4 riders for one reason, traction. By shifting their weight over the tires they are putting more pressure on the rear tires. Like putting sand bags in the back of a 2wd pickup. Still, weight should have been forward.