The biggest mistake I see from the get go is, the Tai Chi practitioner, who was moving back a lot while squaring off, never really engaged the MMA guy who was entering with a lot of forward pressure...which is what a good fighter or someone intent on hurting you will do. When the engagement took place Tai Chi was retreating with no "root" to stand on. Had Tai Chi rooted and entered close enough to suppress the legs then took care of MMA's hands, he could have struck and/or taken MMA down. Instead MMA just bulldozed Tai Chi to the ground like a rock slide.
Ouch! That will leave a mark.
Buy the best and cry once!