The moment Mary Cooper made her entrance in the very first season of The Big Bang Theory, she became a popular character thanks to her hilarious religious comments and always being there for Sheldon.

However, fans couldn't help but notice how bitter she always appeared to be in and wondered why she was that way. Well, the spin-off prequel shows us a different side to Mary and finally explains what was behind her bitterness whenever she came around in the sitcom.

Sheldon Cooper's mother, Mary Cooper, was introduced to the viewers as an overtly devout Christian from East Texas.

Her Christian fanaticism makes her irrationally overprotective at times, and often leads her to deny herself and her family many things to look like a good Christian.

Though she's undoubtedly a witty woman who has raised a boy-genius, we were still left wondering what made her more bitter in than in , where she was less stuck in her ways.

At last, seasons 5 and 6 of shed some light on her life and explained a few important things. Mary's relationship with her kids is far from ideal, and there have been times when fans thought she seemed selfish and hypocritical. However, as it turns out, she had her own struggles, and was, in fact, going through a lot.

Firstly, she was forced to find a new job after being fired from the church when the community found out about Georgie getting Mandy pregnant.

And if you've met Baptist mothers, you'll know that the absolute worst thing that could happen to them was to look bad in the eyes of the people at the church. Not to mention, in a small conservative town in the 80s. So, when she needed support the most, other church members turned their backs on her and made her leave her job, worrying about how they would look. This made her stay away from the community she knew and loved and even began struggling with her faith.

Secondly, Mary and her husband, George, were dealing with a multitude of marital problems, and their relationship was slowly deteriorating.

They had financial difficulties and many disagreements, and we even witnessed his growing attraction to Brenda Sparks, which will most likely lead to an affair.

However, Mary had to deal with her new situation, while everyone else in the family seemed to be moving on. Sheldon no longer had any fears regarding his future, George got his coaching job back and Missy was bonding with Mandy and Meemaw.

The church was the only thing that brought Mary joy, even if she was mistreated there. And there’s no doubt that all this played a role in making her more mean-spirited.