I think this is a one-sided story from the affected employee's perspective. But, irrespective of the employment status of the employee, forced resignation is totally unprofessional and unethical as well. If proven, it would be declared as illegal by the competent court or authority. Yet, how would you prove after a lapse of one year, especially when the management had accepted your apparent prospective resignation forthwith by paying you notice salary from their side?
Since the concerned employee belongs to the senior management cadre, it would be better for him to do dispassionate introspection as to how and where things went wrong because at times efficiency leads to insubordination, but insubordination always ends in incompetence.