As directors for Sears Canada (which is a separate publicly traded stock) they feel that they are being subjected to coercive approaches. It has to be very bad for directors to take the highly visible approach of resignation rather than working it out behind closed doors. Perhaps the behind closed doors meetings did not work out.
Sears has a major governance issue in Canada. The Globe and Mail’s Report on Business (Canada’s major business paper) reports that all six independent board members will be resigning en masse to protest the buyout offer from Sears Holdings (SHLD).