As someone with a passable grasp of both (using ML professionally, and having a wife+friends), here are some 5am thoughts:
1. They're not along a single scalar of difficulty, so I imagine you mean "Why can't I (and some subset of others) master ML but not social skills.
2. ML has large amounts of explicit knowledge, while social skills are largely about tacit knowledge. There are tons of books/videos/etc about social skills too, but they all fall back on metaphors and obvious over-generalizations. It's not (just) because the authors are being lazy - it would take a very long book to capture all the nuance!
3. To extend that point, humans never really figured out a good way to explicitly lay out the rules of language, even though almost every baby picks them up fairly quickly. Language is immensely complex, we just forget that because the human brain is so optimized for it. Social skills are that complexity squared, but (most) human brains are optimized for learning them as well. But writing down the rules as code or (far less efficiently!) a guide book is nearly impossible
4. "It's like everone else has a degree..." I completely understand that. If it's a help, I felt that way too through college. I know you're joking, but let me rephase it: They got good at it because they practiced it. Though you've spent the same number of hours on this earth as your peers, your attention was focused on math/computers/ML, and theirs was focused on observing/gossiping/socializing. Some of them instead focused on working out, and have biceps to prove it. You get what you practice, and you practice what you deeply resonate with.

Again addressing the question I assume you're asking, here's some advice from one nerd to another:
5. Like any academic discipline, you don't need to know everything to be useful. In fact, you begin to see positive results far earlier on the learning curve because people don't value novelty for its own sake. I was largely saved from ostracism by what my parents called 'good manners': Being cheerful, polite, and (by default) quiet. I was definitely considered a nerd, but everyone was nice enough to me
6. You will never be the Prom Queen/King, but I bet you don't want to. Just find a few people who seem to have similar interests and be cheerful, polite, and ever-so-slightly less quiet. If they have anything non-trivial to say about a topic you're also interested in, keep at it! DON'T get discouraged if it doesn't go smoothly - they are probably also learning social skills
7. Have some humility. You might need to buy new clothes, get a haircut, or something else to 'fit in'. Maybe in a perfect world that wouldn't be necessary, but after 18 years of trying you should give yourself a budget of $180 and 18 hours of eye-rolling conformity preparation. People have gone through worse to make it in this world.
8. That doesn't mean that you totally forget about your true self, just that you spend your 'weirdness points' carefully. Be 90% conformist, find the people that resonate with that 10% you're showing, and maybe you can mutually inch down from there until you're comfortable.

Finally, the books/videos/blogs aren't totally useless. Maybe ask someone that you trust which one might be best for you (since it depends on where you're starting) and just rigorously follow the advice for a week. Yes you will roll your eyes, but half of it will work just a little bit. PAY CAREFUL ATTENTION TO WHAT GETS POSITIVE REACTIONS FROM PEOPLE. I put this in caps because I don't have a better way to break it down into actionable steps, and I know it will be hard. But feedback it the core of learning, and I'm going with the theory that you have some (however attenuated) ability to read positive emotions in others. There are literally videos and books on this if you want to practice (remember, you have 18 hours in your budget). Then go out, have a tiny bit of success in a sea of awkwardness, focus on that success, and go out again to have a 'small' bit of success. Then a 'tad' of success, etc. It will be in a sea of awkwardness - don't be discouraged. "Pain is weakness leaving the body" as they say in Crossfit Gyms (you're rolling your eyes again - remember that you've got 17.9 hours of eye rolling still in your budget!)

Anyway, best of luck. It will be hard. You've already done a hard thing, just one that you're more inclined to. If your Prom King could get through algebra (hopefully), you can get through this!