Brenda Sparks split from her husband in Young Sheldon season 4, but why did Herschel Sparks really leave his wife? Aside from Sheldon Cooper's (Iain Armitage) family in Texas, The Big Bang Theory spin-off also features a handful of supporting characters. That includes the Sparks, who live next door to the socially-inept genius' clan.
Before Young Sheldon the existence of the Sparks had already been established in its parent series as their son, Billy Sparks (Wyatt McClure), was mentioned a couple of times. Adult Sheldon (Jim Parsons) revealed in The Big Bang Theory that Billy was one of the constant bullies of his childhood. However, much like a lot of elements in the prequel spin-off, that isn't exactly the case. Instead, Billy is more of a nuisance than an actual bad kid; portrayed as slow but earnest. In recent episodes, he is shown having a difficult time dealing with his parents' split, made worse by Missy (Raegan Revord) turning down his affections. While Young Sheldon continues to factor him into its storytelling as a regular cast member, there is one question the show hasn't answered: why did Brenda (Melissa Peterman) and Herschel (Billy Gardell) really separate?
When Brenda surprisingly told Mary (Zoe Perry) that her husband left, the spin-off didn't elaborate on the reason why, simply establishing that the Sparks have gone their separate ways. But while Young Sheldon hasn't explicitly revealed the in-universe explanation for this, the real reason actually has to do with Billy Gardell booking another sitcom. The actor now plays the lead role in Bob Hearts Abishola, another show from The Big bang Theory and Young Sheldon co-creator Chuck Lorre. The CBS romantic sitcom revolves around Gardell's character Bob, a successful businessman who suffers a heart attack and falls in love with his nurse, Abishola (Folake Olowofoyeku).
Gardell appeared as Herschel in 5 episodes of Young Sheldon from 2018 to 2019, exiting the series after the Bob Hearts Abishola premiere in September 2019. It wasn't until 2021, however, that it was revealed that Herschel and Brenda separated. This didn't pose any serious problems for Young Sheldon, as Herschel only made a limited numbers of appearances during his stint with the character. However, this also begs the question why he had to fully leave the show completely in the first place. Since Herschel doesn't appear regularly, the period sitcom could have retained him for the occasional appearance. Perhaps, Lorre and his fellow producers found this as the perfect opportunity to lay the groundwork for Brenda and George's burgeoning romance.
While Gardell has officially left The Big Bang Theory spinoff, this doesn't mean that he can't come back for a guest spot in the future, perhaps tying a neater bow on his character and his time with the Sparks. Since the actor maintains a working relationship with Lorre through Bob Hearts Abishola, he could easily be asked to reprise his Young Sheldon character. If that's in the cards, it'll be interesting to see his reaction if he finds out that his ex-wife and ex-neighbor are having an affair.