This is explained in the article. Tl;dr for whichever reason these AI bots behave nothing like the web crawlers of old. To quote TFA:
> The current generation of bots is mindless. They use as many connections as you have room for. If you add capacity, they just ramp up their requests. They use randomly generated user-agent strings. They come from large blocks of IP addresses. They get trapped in endless hallways. I observed one bot asking for 200,000 nofollow redirect links pointing at Onedrive, Google Drive and Dropbox. (which of course didn't work, but Onedrive decided to stop serving our Canadian human users). They use up server resources - one speaker at Code4lib described a bug where software they were running was using 32 bit integers for session identifiers, and it ran out!
> The current generation of bots is mindless. They use as many connections as you have room for. If you add capacity, they just ramp up their requests. They use randomly generated user-agent strings. They come from large blocks of IP addresses. They get trapped in endless hallways. I observed one bot asking for 200,000 nofollow redirect links pointing at Onedrive, Google Drive and Dropbox. (which of course didn't work, but Onedrive decided to stop serving our Canadian human users). They use up server resources - one speaker at Code4lib described a bug where software they were running was using 32 bit integers for session identifiers, and it ran out!