DIO is Joestars’ biggest rival in JoJo’s Bizarre Adventure, but he may actually have unwittingly helped a JoJo by granting him a Stand at such a young age. It begins when DIO revives using Jonathan’s body and develops his own Stand. This had a trickle-down effect on the descendants of Jonathan Joestar, triggering the ability to control Stands in Joseph and his nephew Jotaro, shortly before 1989.
This also causes a dangerous Stand type to appear in Joseph’s daughter Holy, putting her life in danger and forcing Joseph and Jotaro to stop the DIO if they want to save her. However, Holy isn’t the only one having trouble with their Stand appearing: the same goes for Josuke Higashikata.
Josuke mastered his position early thanks to DIO
Josuke was born from an adulterous relationship between Joseph and Josuke’s mother circa 1983. Joseph was unaware of Josuke’s birth and thus was unaware that another of his children was in danger. When Josuke was 4, DIO returned. and the Stands began appearing throughout the Joestar line, including Josuke. Since Josuke was still a child, he wasn’t strong enough to handle its manifestation, and like Holy, he was ill. His mother took him to the hospital so he could be treated. It is unknown how much this treatment actually helps, as there is little that can be done for Holy, but one way or another Josuke survived and achieved the Stand, Shining Diamond.
When Jotaro meets Josuke at the beginning of season 4, Josuke is already quite adept at using his Bracket, to destroy things and repair them. He heals a turtle with a broken shell and punches through a woman to hit her captor without harming her. Josuke was able to achieve this feat despite barely knowing what a Stand is simply because he’s had it for 12 years. Josuke practiced a lot with it, especially compared to Jotaro, who only had Stand for a few months before fighting DIO. If Josuke hadn’t had all those years of experience with Shining Diamond, he might not have dealt well with JoJo villains like Kira.
By activating Stand very early in Josuke’s life, DIO has effectively created one of the most powerful Joestars in the series. JoJo’s Bizarre Adventureor at least season 4, would have been very different if Josuke hadn’t mastered his Stand in the first place, and all thanks to DIO.