Browse the modlog and you can see for yourself what they moderate.
Keep in mind that lemmy.world has 7.6x as many active users as lemmy.world, and lemmy.world has 5.9x as many comments as .ml, so that's why it looks like .world has a lot of moderation going on.
As for your question as to why they moderate so much, it's to maintain a strict facade that matches their political ideologies. Censorship, for short.
The censorship tends to stay in the political and news communities, thankfully. There are still a few niche communities on .ml I like and haven't been banned from.