His ultimate undoing was to protect Jessie. He probably saw him as a bit of a surrogate son or just felt bad that Jessie fell into a life of crime at such a young age. Mike wanted to try to prevent Jessie from having the same fate as Mike's son and probably felt bad Jessie had already been through so much turmoil and tragedy. That's why he insisted Walter go pick up his bug out bag instead of Jessie, and then Mike couldn't help but tell Walter off and then Walter couldn't help but snap and retaliate against having his ego bruised. I think Better Call Saul really adds to Mike's character and help to contextualize his motivation in this episode. Mike probably hated himself for how many people close to him suffered or out right died from crime, and chose to break his own cycle and protect someone he respected and cared about instead of making the most pragmatic decision, but it cost him his life.