It doesn't! the real code is pretty much one line in the background.js here: https://github.com/tarla/random-wikipedia-chrome-extension

the other parts are just to add a donate button that redirects to Wikimedia Foundation page

That's from the "tabs" permission; I'm not sure why the extension requests it, as it doesn't appear that it's required by the code (the chrome.tabs API does not require it, you only need the permission if you're reading the URL/title/favicon of existing tabs AFAIK).