The giant gorilla had a forced mutation each time it was close to its death and with each mutation its lifespan was diminished. The first one increased its size and this alone put it on the same strength level as the Sabertooth.
The normal gorillas were from far throwing rocks as help more than anything because this wasn't really hurt that creature the giant one was facing. The second mutation was the surge of silver stripes on the gorilla's fur that acted as Miguel's Magical Circuit. The gorilla had natural enhancement working on its body without any concentration or casting needed.
"WHY? WHY? WHY? WHY? WHY?", the Sabertooth was having a mental breakdown because of the multiple mutations its enemy was having but it didn't know this was on the cost of its own life.
