Basically, after Evo ended (when Grian wanted Evo to end) the Watchers were feeling mischevious and when all the members wanted to defeat the ender dragon, they were all sent to individual fights.

When everyone came back, one was missing, and it was Grian.

The life series is basically a repeating cycle of death games and the Watchers are the ones orchestrating it.

After Grian left, there was a new entity called The Listeners

The Listeners weren't happy at all with the Watchers

Back to the life series

The life series is basically the Watchers punishing the former Evo members (only 4 are actually members) for trying to flee with the help of the Listeners

Grian became a Watcher, and he now inserts himself into the games to be a bit of a nuisance.