You was loaded really heavy with that ash...
I don't know what your ATV is spec'ed out for load carrying capacity...
I would bet that on level ground you would have been OK...
We just purchased a used Toro Workmaster for our baseball fields at the park and I think that it is rated for 850# load capacity...
On level ground it does fine but I've never tried to pull that kind of load up a hill...
The belt drive automatic transmission is not best suited for extreme pulling...
Don't be too hard on yourself or your ATV...
It is a good machine...