The Gray Matter storyline happened at least 20 years before the events of the show began. There's no indication he would have broken bad/lashed out due to this, by all indications he led a normal life since then and is seen by everyone he knows as a upstanding, somewhat meek but respectable person with no outward character flaws.
The cancer diagnosis and its implications for him and his family is what sparked this. And he continued further down that path due to believing he was going to actually die. If you recall when he decided to get treatment and found out he was in remission, there was a moment of "wtf have I done" for his character.
The Gray Matter backstory, and his former cofounders re-entrance in his life due to perceived medical bills explained the peeling the onion that led to his shift.
The cancer diagnosis and its implications for him and his family is what sparked this. And he continued further down that path due to believing he was going to actually die. If you recall when he decided to get treatment and found out he was in remission, there was a moment of "wtf have I done" for his character.
The Gray Matter backstory, and his former cofounders re-entrance in his life due to perceived medical bills explained the peeling the onion that led to his shift.