Why did I not have front wheels spinning?

[tomp]

At part throttle, nothing was spinning. Then, when applying more throttle to make it over the top, the rear would break loose and spin. Fronts never would move while rear was spinning as both fronts were on the ground and I was sitting still.

Only way to make it over was to reverse and build up some forward momentum.

Also tried slightly mashing the brake during throttling and that did not do anything