These are the 15 most recent “Last seen” in my forum (very little presence, as you can see), but the consolidated pageview graph indicates an outstanding 281 logged in users just five days ago, on November 13th:
Those are pageviews by logged in users, not by different logged in users. So if you, for example, navigated the site a lot, this could be all caused by you. I had more than 500 pageviews per day, all by me when I explored the settings of Discourse.
You can find more information at the Documentation topic: Understanding pageviews and the site traffic report
Crawlers are programs that index content on the web, for example for search engines.