It's a bit suspicious because a) he just said two days ago that he has no intention of stepping down from GNU https://lists.gnu.org/archive/html/info-gnu/2019-09/msg00008... and b) there's another copy of the entry dated yesterday, deeper on the page: https://stallman.org/archives/2019-jul-oct.html#27_September...
It 100% wouldn't surprise me if he didn't have adequate security for his personal website. He comes from a culture of leaving doors unlocked and passwords unset, and he also doesn't actually participate in the modern web (he has a daily cronjob that emails him text dumps of web pages he wants to read, he doesn't "browse" the web in any me), and his personal site is probably not actually run by the FSF or anyone else with experience in running websites.