Activitypub suffer from virality, it doesn't offload. The original hosting server always gets pinged for every interaction. Meanwhile AT protocol is capable of simply acting like a series of pure mirrors so a self hosted PDS (account host) doesn't get tanked if you get flooded with replies and reposts and more, as the appviews does the job of indexing those responses and your client only need to look at the index (threads, like count, etc) it produced for you.

Jekyll simply creates and updates static HTML files. Git for version control. Multiple sites (including github pages) can natively publish that format of static files as a website.