Pretty much when the flock of fresh MBA grads seemed to take over the marketing dept and started making significant business decisions... remember the brilliant ideas to remove desks from hotels and leave no place to actually work, since they were going after millennials and figured they'd just lounge on the bed and play on their phones? Then the whole change from marriott rewards to bonvoy... ugh, we know how that went (and is still going).
Unfortunately that also coincided with the Marriott family stepping back from being directly involved with daily management decisions. Its a shame whats happened since Bill stepped back from his involvement.