Explain Like I'm Five

There's a lot of things. Some scrapers aren't smart and will grab every link they see, just in case. Those links will often be redundant, but the scraper might not know that until it's done downloading it. A 1MB download doesn't seem too hard on the server, but do that a thousand times a minute and that's a decently heavy load on any small website. I saw a creator talking about how they noticed AI bots scraping their website since they had literal decades of code that was well documented and guaranteed AI free. The bots could easily grab the git files and have all of that code with every commit message for about 4GB. But instead the AI was asking the Website to render each and every commit as a webpage which took a 0.5KB change and rendered it as a 5MB webpage since it showed all the code before and after, all the formatting for a webpage, etc. This meant that each scraper was downloading TERABYTES of data from his website when all it wanted was in a nice, single download that was in a very computer-friendly format to parse. None of these scrapers were made smart. If they were, we wouldn't notice them. It's because they're dumb, but spending a lot of time and money on "avoiding detection" that it's dangerous.

Legit I had a website give me a 403 on an API request earlier. They had changed their API to block anything trying to masquerade as a browser. They actually just wanted legit API users to send a user agent that had a username and a project name. If you pretended to be a browser, you got blocked. On the 403 page, they had a direct link to download their whole database in one go if that's what you wanted. They had links to the database on megaupload that was updated every 24hrs, and then a patch database that listed all the recent changes to keep you up to date. Literally they don't care if the data is taken. What they cared about is wasting their bandwidth and trying to be sneaky about it.