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.
I saw someone made an International community but couldn’t find it on my instance, so I made a Lemmy.ml one
Your home instance will only receive posts to a community on a remote instance once at least one user on your home instance is subscribed to that remote instance's community. If you're the first one, you need to trigger a search for it, then subscribe, and then your home instance will start getting posts.
I'm going to go to Lemmyverse's community list to search for it:
The community international does not exist on this instance (yet). This can happen if you are the first person to try and open it in this instance. Someone will need to prompt this instance to fetch the community from the original instance. This task can be trigerred by entering the community URL (ex. lemmy.world/c/international) or identifier (ex. !international@lemmy.world) into the search page (reference).
You can do this by clicking on the button below, and then coming back after some time. Don't worry about the "No results" message, the fetch process would have started in the background. Alternatively, you can copy one of the codes above and do the search manually at https://lemmy.ml/search. You can also just view the community on the foreign instance.
If you want it to, go to the above link I made to your home instance's view of the thing, click "trigger a search", and then subscribe to it, and if/when people post there, you'll get posts.