A popular fan theory in GTA San Andreas suggests that Ryder wasn't always meant to be a villain.
Think about it for a moment: During "The Green Sabre," who does Sweet and CJ keep mentioning after the big reveal happens? It's always about how astonished they are that Big Smoke would do this. Yet, Ryder was there with him, and he was clearly visible; not a single mention. Even if Big Smoke were more important, it is still bizarre that Ryder's importance and existence fizzled out until his eventual death.
That's why there's a popular fan theory that suggests Ryder was never meant to be an antagonist in the first place. In fact, there's some strong supporting evidence in favor of this fan theory, which makes it a lot more credible than some other GTA San Andreas fan theories. Perhaps Ryder wasn't always intended to be a villain in GTA San Andreas.
GTA San Andreas fan theory: Ryder wasn't meant to be a villain
Ryder and Big Smoke are two old friends of Sweet and and CJ, having been members of Grove Street for a long time. However, the two eventually sell out Grove Street in favor of working with CRASH and the Ballas. In Big Smoke's case, it's heavily foreshadowed and referenced after the big reveal. In Ryder's case, there's honestly not much except for the introductory movie released after the game.
It should go without saying that Big Smoke was unquestionably meant to be a villain. There are a lot of hidden signs the player can see at the start of the game that support it, and the game makes is abundantly clear that's he an antagonist as he's referenced alongside Tenpenny plenty of times after "The Green Sabre."
Just for comparison, this GTA San Andreas theory will compare Ryder's involvement with GTA San Andreas to Big Smoke's. This fan theory isn't total hogwash; there are some valid points to suggest something changed mid-development.
Where Ryder lives
Ryder lives in the heart of Grove Street, right next to the Johnson House. By comparison, Big Smoke lives near the Ballas in Ganton, nowhere near his Grove Street homies. It's a small sign, but a minor one to note. If Ryder wanted to distance himself from Grove Street, living in it wouldn't be the brightest idea (even if Ryder wasn't the smartest fellow).
Ryder's missions are all about helping Grove Street out. Whether it's stealing weapons from the Army or sneaking into an old colonel's home, his missions in GTA San Andreas make Grove Street stronger. Once again, it isn't logical to make the group you plan on betraying even stronger.
Compare that to Big Smoke's missions, which often benefit CRASH or the Ballas. He's constantly fighting the Vagos and the Russian mafia, two groups which often pose a threat to the Ballas. Note that none of his missions in GTA San Andreas directly involve making Grove Street stronger.
As legendary as Big Smoke's order is in and outside of GTA San Andreas, it's a clear example of him making an excuse to not attack the Ballas (as well as stall for longer enough so the Ballas can get into position). During the mission, Big Smoke never shoots at the Ballas, while Ryder does. Ryder even mocks Big Smoke for not shooting.
In other missions like "Just Business," Ryder has no problem squaring up against the Ballas. He doesn't make excuses like Big Smoke, despite the fact that it could complicate their relationship with the Ballas.
Ryder is often abrasive and mocks CJ for leaving Grove Street. Funnily enough, Sweet does the exact same thing at the start of the game, so it's likely a common sentiment felt throughout most of the loyal Grove Street members. Big Smoke, predictably, isn't like that. Strangely, Big Smoke didn't attend the funeral, while others like Ryder and Sweet did (at least until CJ entered his home).
The GTA San Andreas fan theory
These minor points help support a case that Ryder wasn't meant to be a villain like Big Smoke was, but there are far more significant cases to be made. Particularly, in how Ryder is practically never mentioned again after "The Green Sabre." Considering how shocking the betrayal is, fans often wonder why CJ and the gang completely forget about Ryder and focus solely on Big Smoke throughout GTA San Andreas.
The simple case could be that Big Smoke was always meant to be the villain that betrayed Grove Street; there's no arguing that. However, it is likely that Ryder was only added as a villain later on in the game's development due to a conflict involving his voice actor. Rather than have him disappear, they decided to have him randomly betray Grove Street, just to kill him off anticlimactically later on in GTA San Andreas's storyline.
Nobody mentions him
The strongest case for Ryder not being a villain originally is that nobody mentions him when he betrays the gang. Literally not a single person from CJ to Sweet mention it during the mission. All of the focus is on Big Smoke throughout GTA San Andreas.
While Big Smoke is smarter than Ryder, it would be strange for a childhood friend like CJ to completely ignore the fact that his homie might've been involved in his mother's death. All Ryder gets to say is "I'm a motherfu**ing genius." in his final GTA San Andreas appearance.
What some fans would've preferred
Although it is difficult to work with a character without his voice actor present, some fans propose the idea that Ryder should've just died as a martyr for Grove Street. It would've been more in-character for him, and he wouldn't have to be blatantly ignored whenever the betrayal was brought up in GTA San Andreas.