Reading into the Wikipedia sources it seems the type of sealant used was liked not cured sufficiently before it was exposed to the elements. (Makes sense, the average pool isn’t getting cooked in direct sunlight like the reflecting pool was).

It’s like a home chef trying to cook in an industrial kitchen for 1000s of people. Trump’s pool guy just repeated the process used for personal pools on a project way beyond the scale they were qualified for. Shit didn’t work how they expected it to in a completely different climate and and scale.

It short. “Trump’s friend” was completely unqualified. Shocker.