The video looks like the player started the argument very face to face which in the covid age doesn't seem right. Then the umpire tosses the player and walks away. The player pursues the umpire and they get close again and the umpire appears to have laid his left hand on the players should or chest and gets shoved hard enough to lose balance and fall backwards rather harshly as if they didn't have control of their balance and couldn't properly fall.
That is my initial take. I am sure there is more to the story. But we don't have sports without umpires and we don't have umpires if they are not protected.