Not funny this time...
I believe Gen. John Kelly was channeling his own grown deceased son killed serving his country; when he supported Rob Porter & looked the other way from the abuser.
Gen. John Kelly's past pristine achievements before Trump has nothing to do with a blind spot that comes after you have lost a child - no matter how old he or she was.
So, it doesn't matter what Kelly knew & when he knew it; he knew it, but unconsciously blew it off - in this case, the heart knows no time table.
Whether Trump accepts his resignation is not here nor there; considering the source but, in matters of our (homeland) security & propriety under Trump's reign, such as it is - it's time to clean house.
Trump's unconscionable non-action, on the other hand; has already been examined & explained ad nauseum in every legitimate forum.