Why did the Firefox Homepage Facebook shortcut send me into a never ending login/Captcha loop?

I clicked the Facebook homepage shortcut instead of using my regular bookmark. The page eventually loaded to the login screen, which then led to a Captcha verification screen, and another, and another, etc., until I got back to the login. Whew! Okay. No, not okay, it prompted me to get a verification code by email. I entered the code to log in. It started again. Then again. Cleared cache, etc, restarted browser, all the usual, didn't help. I had to leave for work.

When I got home, I restarted my computer and reset the modem. I removed the homepage shortcuts. Used my regular Facebook bookmark and logged in. Why did this happen? I am now terrified of the Homepage Shortcuts! 🤡💀