...any idea what that it's all about or the purpose of them doing it so heavily?
Scraping your content, copying your website, harvesting your image files, retrieving data about the way your server handles requests, indexing your website for whatever utility they are promoting or selling... take your pick. Information is money. Chances are since they are hiding in the cloud, they are up to no good.
Several agents from what has been labelled as the "Twitter Swarm" are spin-off businesses that compile Twitter activity. Probably harmless except for the fact they are making a profit using your (and everybody else's) tweets/links.