At risk of not reading all the comments, the lion is smothering the buffalo. It's their M O, MODUS OPERANDI!!!
When they get the prey down and it's still squirming one female goes for the kill by smothering , cutting off all airways. Mouth and nose!!
Females are the bad asses of the lion kingdom. The lazy male is back grooming his mane waiting for his lions share of the kill. And that also means he eats first and as much as he wants.