Why does Mike commit suicide in the ending of GTA5 Kill Mike?

Remember, the mission of Mike’s suicide is called the causal loop, which is exactly what it means. In the early days of the game, during the North Yankton mission, in order to get rid of this life of wandering and murdering people, Mike cooperated with FIB agent Dave and "rebellion" with the robbery team, resulting in the killing of Hillbilly and Brad. Trevor didn't know Whereabouts

As you can see from the subsequent plot, Trevor has always remembered him and believed that it was his fault that caused Mike's death. He met Mike again in Los Santos, and as the plot unlocked, he also Gradually, it was discovered that Mike was deeply deceived and betrayed in the robbery nine years ago. Therefore, he felt very angry. When Mike saw that Franklin did not kill Trevor, who was like a madman, but instead came to him, I guess Mike felt like this. The name of this level's mission is the same, cause and effect loop. It's also a betrayal. Mike betrayed the team and deceived Trevor and Brad; Franklin betrayed Mike and came to the door with a gun. Therefore, Mike may think that this is retribution for what he did nine years ago. Therefore, psychological despair and collapse, instead of dying under Franklin's gun and dying in the name of punishment, it is better to commit suicide and get some redemption and peace of mind.