If you backup Obsidian and ICloud and your plugins and styles disappear.

Obsidian stores all the plugins, all your fancy styles and settings in the .obsidian folder in your vault.

I have set my MacOS to “optimize storage”. So infrequently accessed files are stored in the cloud and not locally anymore.

So Obsidian can’t find it.

To work around it, go to your vault folder, right click and press “Keep Downloaded”.

That’s it.