To take control of other people’s content and, by extension, revenue streams? Performance was a selling point to the web dev - me, as a user of the web, was never even asked my opinion, and I can’t (easily) disable amp.

Alphabet cared. It cared about what corporations can care about, making money. It invested so much because there was a good return on investment and there was a lot of cash on hand wanting for investment and Amp was big enough to make use of enough cash in hand to be worth pursuing. With billions of cash on hand fixed overhead makes small investment not worth the bother. For Alphabet, a hundred million dollars is less than rounding error.

To compete with Facebook in centrally controlling the internet and the revenue that flows through it. It's their Plan B after their Plan A, Google+, failed.