I take reddit fan theories with a grain of salt, but I did see an interesting theory about Cypher. To summarize, they speculated that Morpheus may have originally thought Cypher was a candidate to be The One. This could explain a couple of things.
assuming his character is the same age as the actor, he also would've been freed as an adult, going against the general rule about only freeing the young. Joe Pantoliano is even older than Keanu Reeves, and Cypher says he was freed 9 years before the Matrix. Neo is what, like 25-early 30s when liberated, and if we assume Cypher is at least 10 years older than Neo, he would've been an adult when freed. Why would Morpheus free an adult knowing the risks, unless he thought he might have found The One? Unless that rule was a rather recent thing. This previous finding of what he thought to be The One, only to realize nope he didn't find him, and in addition had risked a lot in liberating an adult, could also explain why some in Zion were very skeptical about Morpheus' beliefs and continued insistence on finding the real One. They're seeing Morpheus find one false One after another, so by the time he finds Neo, the skeptics like Commander Lock want to hear nothing about it.
Further, this could explain the seeds of Cypher's bitter feelings, having been previously told he might be The One, only to later find out this was bunk. Hell, maybe trinity, having been told she would love The One, might have tried flirting with Cypher or iniotiating something, only to break it off once it was decided he wasn't the one (hell, she probably just wasn't feeling it, and so this could have contributed to Morpheus realizing he was not the One, assuming trinity told him about what the oracle told her). Even more salt in the wound after seeing Neo found and the woman he loves almost immediately start to fall for the real One, while Cypher had been reduced to little more than one of Zion's rank-and-file soldiers. For someone who cares so much about his status, that would be pretty crushing to his ego.
I strongly doubt the Wachowskis had something like this in mind, but an interesting theory nonetheless
* * * *
I'm imagining a prequel where Cypher takes a similar trip to see the Oracle, only she actually tells him "yes, it's you." This is kind of in character with how she tells Neo "nope, not you", and I could see it almost being a test. Once he hears this, it goes to his head, and of course it's in his increasing narcissism and sense of self-importance that Morpheus eventually realizes Cypher cannot be the one, as he cares more about his own status than anything else. When Cypher realize Morpheus has lost faith in him, this of course makes him bitter, but otherwise he continues being loyal. It's only when Morpheus brings his new prodigal son on board that Cypher snaps and decides to betray his crew.
For all we know, maybe Cypher is one of the reasons they established the age limit rule in the first place.