Well, no one knows for sure but my guess is:

1) He did not resign for health reasons or they would have said so.

2) He did not resign to retire or they would have said so.

3) He left amicably, was not "fired" or they would not have kept him on as a consultant.

4) He is not leaving to go to a competitor as again they would not have kept him on as a consultant.

5) My guess is he had the opportunity to serve as CEO somewhere.

6) Another guess is it is a cost cutting move by JT but that seems unlikely in the face of the LPC funding.

7) The reduction in the board seats to five? Cost cutting maybe but again LPC? Increases Epics influence? A board of 5 can't have a split vote?

Just some out loud thinking. Hopefully there will be further announcements to make the picture clearer.