He ain't quitting. He's just overwhelmed and exhausted due to having to manage the company as well as shooting videos. His company is so big now that he doesn't have time to do other things, like spending time with his kid.
It's amazing how LTT has grown so big and in such a short amount of time. Although he can afford to retire, he ain't gonna quit now when LTT hasn't peaked yet. He mentioned that there was a kid from Make-a-wish that wanted to see him, but due to scheduling conflicts he couldn't go visit and instead made him a video. The kid passed away and his father still thanked Linus. This made him a have a mental breakdown as he realized he has been so busy that he needs to spend more time with his kids.