Thing is, Google requires an absolutely stupid amount of computing resources for running their core business. YouTube transcoding is a great example and a big one for sure, but I bet they have even bigger ones in there somewhere. I have no real data to base this on (and I'm sure nobody does), but I'd bet 5:1 odds that if Google were an AWS customer, they'd be bigger than all the others combined.
So in that case, optimizing for a single customer makes perfect sense if it's the right customer.
So in that case, optimizing for a single customer makes perfect sense if it's the right customer.