[corin_]

Firstly a pedantic point, he played 7 letters not 8, but his 7 made an 8 letter word.

I don't play scrabble more than once or twice a year and am not great even by playing-it-with-family standards. But the concept that not using all 7 of your letters leaves you with a potentially bad next hand is one part of their overall strategy, according to the article. They also will be thinking about what letters are already gone and therefore what might be left to draw, they're thinking about what opportunities they might be opening up for the opponent, and they're thinking about their future opportunities too. And of course they're thinking about how many points they'll get, too.

His Bingo (I never knew that was a thing in scrabble before today) scored 72 points, so if he can find a way to justify it, it's something to at least consider. Looking at the board when he played it (and including the 7 tiles he put down), there are five clear spots where there is an open vowel with space to become a 4 or 5 letter word, which might make him worry less about not pulling a vowel if he reloads his letters. Add in all the other strategic thinking he has and I don't, I wouldn't be surprised if he made an intelligent rather than lucky decision. Of course, with his next draw, he was lucky that not only did he get Q and Z, but he also got a blank. But every time you get new letters in scrabble you're going to be lucky or unlucky, regardless of how well you play.