What I saw in the close up video was that is was coming in way too fast. I would estimate 30 feet per second within one booster length of the barge.
Then, the X/Y velocity was not zero and had to be corrected at the same time.
Too much, in too little time.
Musk needs to pull this off, having more fuel and burning it to zero the X/Y higher up and reduce the rate of descent higher up. Not by much. They know this, but don’t want to reduce payload.
Armchair engineer.
That won't do because the thrust/weight ratio is >1 even at minimum throttle. They throttle back too much and the candle snuffs out with no time for relight. 30 fps at 30' is no problem to zero, the trick is to do away with the horizontal motion and have that last 30' be straight down to the pad.