It's not my opinion. It's literally in the site rules - https://support.reddithelp.com/hc/en-us/articles/360043504051 Bullet point 2 in the second list. Bullet point 3 arguably also applies since lemmy could be said to be unrelated to the subreddits in which you were posting. And when site wide rules get broken then it's the admins that step in, not subreddit moderators.
Edit: As for the self promo part I mentioned in my previous comment, that would fall under bullet point 2 of the first list in the link. While you may not actually have a stake in lemmy, your actions on reddit definitely made me suspicious that you did before I looked into lemmy more and learned who the the heads of the project are. It would have been easy for a mod or admin to have seem just your comments on reddit and assume the same thing.
I'm not saying I disagree with your motives but your actions were pretty clearly breaking long established rules.
There are plenty of other reasons to criticize reddit. Enforcing their existing rules is not one of them.