There are several issues here.

The lemmy instance thing is because people don't like being spammed by onlyfans ads, torrents of AI generated porn spam, deluges of random penises men are happy to post assuming lots of people want to see it, and in some cases operators have ethical objections to porn production itself, or don't want to deal with the possibility of rehosting and being responsible for content containing minors being hosted on their services and the legal headaches that entails.

The last one about legal problems has arisen due to increased awareness yes but also increased pressure. The amount of hosting companies out there who look the other way for violations are fewer and fewer by year out of their own fears from payment companies, technical partners, etc. Even accidentally hosting that stuff besides the risk of getting you raided by cops at 2am and having your whole life gone through (while automatic weapons are being pointed at your face) could lead to your hosting being terminated and having to pay more and more each time that happens as you move up from the cheapest hosts to the ones left. It's also a hassle to move.

Censoring tarot cards, swear words in memes and on TV that's an example of corporate prudishness. That's an example of fear of upsetting advertisers, of people self-censoring to go viral, to avoid Zuckerbook removing their post and actioning their account because Zuckerbook has this weird notion of being family friendly and appealing to advertisers. So much of that lays at the feet of advertisers and Christian pressure groups who exist to beat the drums of fear of losing advertisers and pressuring those same advertisers to pressure the tech companies.

It's about risk compliance for those tech companies as well. Your bank would rather close all your accounts and refuse to do business with you ever again if you have less than several million dollars with them if you bring too many automated red flags. They won't care you have half a million with them, they won't care you protest your innocence, even the chance the system is right in flagging you a risk and getting hit by authorities leads them to a behavior similar to self-censoring where they self-police overly aggressively out of fear because you're just not worth the trouble and risk.

In the same way these companies don't care about artistic expression, they don't care about freedom of speech, they care about maximizing profits and that means minimizing compliance risks, minimizing risks of being legally actioned because there's even a chance what you shared could turn out to lead to legal liability, and minimizing risks of upsetting overly sensitive prudish customers and advertisers.

So at it's core its driven by a capitalist drive to avoid government scrutiny, fines, interventions, and by that same desire to offend the least amount of people and not upset advertisers by placing their ad for a new burger next to erotica art or bared human body parts or naughty words.