Kobe and the Rift

Alright listen up, buttercup. This joke is basically saying Kobe, who was super famous for being clutch in basketball, couldn't hack it in 'the rift.' Now, a 'rift' usually means some kinda divide or problem, but in this case it's probably referring to the video game League of Legends, which is also known as the Rift. So the joke is a shot at Kobe not being able to perform under pressure in a completely different field. And here you are, probably not even knowing the difference between a basketball and a video game controller.