His error was ignoring the 2 inch tree in the way and attacking the 10 inch tree. Pushing over tree's with a tractor is doable. You just have to be very very careful. There are several dangers, Never push over dead trees, they always break off up higher and fall on your hood or your head. Never ram a tree, apply power slowly. Dont overdo it, by trying to push over too large a tree, and breaking or bending something. Push trees a couple of days after a rain, preferbly, so the upper soil is firm, but the roots are still in looser wetter soil. Look first for widomakers or dead branches liable to break off and fall on your head. But if you dont feel comfortable doing it don't do it. Now again his error was not removing the 2 inch tree and keeping his work area clean before he attacked the larger tree. Always clean your work area, as you clear land, never leave anything that your tractor has to work over, be that small trees, large rocks or holes. Clean and repair, then move forward for the next victim.
One advantage to pushing over trees is there is no stump left to deal with.
James K0UA