I’d guess that bullet ticked something on the way in and was helicoptering on impact. Seen same thing on a white tail doe , with a 30’06 and 165 gr TTSX @70yrds. Appeared broadside but must have been slight quartering to. Hit a willow about 10’ from doe, spun in helicoptering tore a hole like that from front shoulder down the inside of the ribs and wound up in rear ham. Pretty much ruined the complete half of deer. Huge entrance like above and the bullet recovered in the ham could have practically been reloaded again. Nose had a slight bend tip was missing.. sometimes bullets do strange things.
I’ve also learned the sight picture often changes SS you near a downed animal. Often little brush and shrubs that didn’t appear in the scope are present. File it under [bleep] happens , you could take that same shot 100 times over and never duplicate that exact result.
Bullet hit nothing but air between the muzzle and antelope as it was wide open prairie. Antelope was quartering away so we just figured the bullet hit and changed direction back out. Chalked it up to crazy stuff happens....
Two years later he shot this cow almost broadside at 370 with a 6.5x284 and 130 Accubond at 3,075 muzzle velocity. Bullet passed through and she went maybe 30 yards. Great performance.