How to create a folder symlink that has a different name?

You already have a directory at ~/.pm2/logs. Since that directory exists, the symbolic link is put inside it.

Would you want that ~/.pm2/logs is a symbolic link rather than a directory, then you will have to remove or rename that existing directory first.

As other answers say, there is already a directory there.

To avoid this and instead get an error-message, use the -T option, unfortunately I don't think this is Posix (it is GNU).

From the Gnu ln manual (same for cp and mv).

   ln [OPTION]... [-T] TARGET LINK_NAME   (1st form)
   ln [OPTION]... TARGET                  (2nd form)
   ln [OPTION]... TARGET... DIRECTORY     (3rd form)
   ln [OPTION]... -t DIRECTORY TARGET...  (4th form)

Note form 1 without the -T is ambiguous with form 3 (both have two arguments).

In Posix you can force this non-ambiguity by putting a / at the end of a directory name, in form 3, but I don't think there is any thing you can do the other way around. This is why Gnu added the -T option.

Remove the ~/.pm2/logs directory first, because your target is an existing directory, the link is created inside it.