During the time when their marriage was on the verge of dissolving, she delved wholeheartedly into religion, while he fell headfirst into “a bottle blonde bartender” who tried to buy Sheldon’s affection with action figures.
Both of these things contributed to the breakdown of their marriage. Both of these choices, in the end, were responsible for the dissolution of their marriage.
In the episode titled “The Rhinitis Revelation,” Mary and Sheldon make a veiled reference to the possibility that the reason he passed away at the age of 50 was because of obesity-related health problems that were brought on by her cooking.