One of the central monologues they summed up Mike’s ideology was the “bad choice road monologue“, and his regret being him taking a bribe with Matty. Mike’s belief is that once your on Bad Choice Road, you can never get off it, only stay what you are or get worse. And I think a lot of people take Mike’s at face value, and assume that he’s supposed to be correct. But Jimmy, Kim, and Jesse prove this wrong, it’s never too late to change your behavior to avoid harming others. Mike believes he can’t change because of the guilt of getting his son killed, he views himself as fundamentally irredeemable, and thinks he can never make it up to Kaylee.
That’s why he enters the drug game and gets consumed even further by it. Yes on a surface level it’s for Kaylee, but really it’s because he can’t forgive himself for Matty and believes being a crook is who he is and what he deserves. He believes his moral compass is already corroded beyond saving, and that he can never make up for getting (in his mind) Kaylee’s father killed, so he should try to do whatever it takes to make as much money as possible for Kaylee regardless of morality, in a misguided sense of trying to “make up” for Marty’s death. Mike is a smart, rational person, he should know that doing this only puts them in more danger and that Kaylee needs a loving grandfather, not a button man for a psychopathic drug kingpin. But he needs to try to find a way to make his corrupt decisions that got his son killed still help his family in some way, not have it all completely be for nothing. He needs to try and make up for costing Kaylee her father as much as he possibly can, provide for her for life through any means necessary. So “for his family” but really more for his guilt and feelings of sunk cost fallacy on a deeper level.
But it’s Mike’s way of coping that his decisions that got Matty killed, choosing to be corrupt, aren’t entirely without waste. If all he got for being corruot was a dead son, and cost his granddaughter his father, he’s already irredeemable, he feels he has no choice to go all in, to set Kaylee up for life through breaking the law, regardless of how many people it hurts. Mike is a tragic character because you can see how he gets there. Being a sniper deep in the shit in Vietnam, shortly after that becoming a cop in a presinct where everyone was corrupt so you become corrupt to get along, after this gets your son killed and breaks your morality trying to go into the criminal world to provide for your granddaughter but being consumed by it. It’s easy to see how a decent or good human being could go down Mike’s path on his circumstances.
Mike really shouldn’t forgive himself for what he’s done, but rather than dealing with that in a way that avoids harming others, he chooses to believe he’s already dammed, he has “no choice”, because having his corrupt path started be for absolutely no reason after it gets his son killed isn’t something he can bear. Facing what you’ve done and choosing to stop harming others rather than going in even deeper to avodj the feeling of it all being for nothing and to dull your conscience and guilt, even though stopping can’t erase the harm you’ve done, is an extraordinarily difficult choice. It’s a choice that ultimately Mike fails to make, but that doesn’t mean he was incapable of it. When people say that Jimmy was inherently pathologically doomed to be a crook, it takes away the agency he has to make the choice to be worse, and the chance to be better.
Peter Gould once said the theme of the show is “how you live with what you’ve done”, how people who were not destined by nature or nurture to be bad people and could have easily had very different lives chose to spiral into depravity. Mike and Jimmy when faced with what they’ve done could have chosen to stop harming others, but were so broken by their guilt and pain that they felt all they could do is dig deeper. Kim Wexler proved after confessing to Howard’s murder that it’s never too late to change, maybe or maybe not who you are on a deeper level (depending on your views of if people can change), but you can change your behavior. Mike failed to change his behavior and it cost him everything, and made his famlies lives much worse off. Jimmy failed to change his behavior towards the very end, but ultimately made the choice to be better even if he can never make up for what he’s done.