You don’t need to follow someone to see their content. When you open the app the default timeline is the “For You” one. Sometimes you don’t even notice that the app has switched back to “For You”, X definitely doesn’t really want you staying on the “Following” tab.
"Popular" tweets (of which these bot accounts often fall into, because they're propped up by bot responses and engagement farming) are pushed into your feed even if you're not following (or engaging) with them.
