disaster turns out OK

My first attempt at using Maris Otter in a SMASH brew had all the potential of becoming yet another disaster.

When I mashed in, my initial temperature in the MLT was 168F. I tried three times to add cold water to bring it down, but for some reason it didn't work. I was convinced I was wasting both my time and my materials.

After drinking two bottles, I am completely amazed at how it turned out. The bitterness seems to be a bit higher than planned, but that will mellow out as it conditions in the bottle.

How can a mash be so much higher than planned and still convert so well?

Your mash ended at 168°F?!?! What did you calculate your strike temp at and what were the temp of the grains?
I just did 17lbs of grain at 78° and my strike was 5.5 gal at around 163° for a 10 gal batch. Sounds like you missed your strike temp by a country mile.
Also it would be nice to know what your planned FG was vs actual. Seems to me that if your thermometer was reading correctly, then your beer would end up pretty sweet.... Actual, REAL sweet and malty.