Dramatic increase of direct traffic and robots

I have several sites connected to cloudflare.
Since the end of April, one site has seen a dramatic increase in direct traffic.

It was very strange. Then I discovered that this traffic is generated by robots.

Then I found that the same situation happens with some of the other sites that are added to cloudflare, but not with all of them.

Then I turned on the Security → Bots function. But it didn’t help at all.

The next step was to change the Cloudflare DNS for one site’s domain to my server’s DNS.
And the robots immediately disappeared.

What’s going on?

You mean direct-to-the-server-IP?

No. Direct traffic is when users get to the site not by link, not from a search engine, but by typing in the site address or coming to the site from bookmarks in the browser. The same happens when bots visit the site.