"It feels like I have spyware on my computer."
Oh, it's much worse than that. There is spyware on everything but your computer, probably.
Grapeshot is an Oracle service. Here are a few quotes from the crawler explanation page:
Oracle Data Cloud assists advertisers placing contextual advertising
on web pages.
Pages are only visited on demand. If Oracle Data Cloud Crawler has
visited your site it means that an ad was recently placed on a page
where the information was either not yet available or needed to be
refreshed. For this reason, you will often see a request from Oracle
Data Cloud Crawler shortly after a user has visited a page.
That means you probably have ads running on the page. When you visit the page, Grapeshot and other crawlers also visit. Basically, your ads ratted you out and now the crawlers want to know what this secret page is all about.
A significant chain of systems may cause Oracle Data Cloud to analyze
your site. Oracle Data Cloud Crawler provides real-time contextual
information to a number of Real Time Bidding (RTB) systems, such as
Rubicon, AppNexus, and more. These RTB systems are often used by
third-party ad server systems as part of their ad serving strategy.
I like the way they worded this. "A significant chain of systems" is their way of saying "we don't feel comfortable listing all of the reasons for a crawl."
The other two crawlers are most likely there for the same reason. You can block the crawlers, but it could cause problems with the ads if this reporting is required. I would leave them to do what they want unless it's a problem (stressing your server).