If that information is true, meaning that the entire board of directors resigned, it's indeed unusual and worrisome. It's certainly something to keep an eye on and would be subject to scrutiny, given that the board of directors has a dual role. It has a strategic role, of course, but it also has a fiduciary role. There are certain expectations of stability and expertise of a board of directors, to ensure the organization has proper governance.
It's rare and worrisome to see an entire board of directors resign collectively or, rather, simultaneously, since it wasn't necessarily coordinated.