Games and SoMa apps want to keep your attention as long as possible. To do so, they load up on things that activate little dopamine rewards for the users. A simple thing is simply the accumulation of some kind of reward. Is there any difference between coins and likes?
One of the most powerful dopamine reward is when we see something that reinforces a core belief. Once a SoMa app discovers a user's core belief it can algorithmically present content that reinforces that belief to keep the user scrolling. This effect is more pronounced the more "out there" the belief, which is why conspiracy theories and disinformation thrive with SoMa.
But there is a second thing that the SoMa apps do that is only really coming to light, but that was seen in games first. By creating a collection of followers, the SoMa apps create a progression. Progression is big in games: characters gain levels, gain loot, access new areas etc. The progression creates a giant sunk cost for the user over time, which makes switching from one platform to another way harder.