And get sued by Google? You aren't allowed to use them to train anything that could compete with Google's business or products as part of the usage agreement.
Citation? I did a little digging of my own, because I found this claim to be uncharacteristic of any company I've ever worked for. I did find some restrictive clauses, but I don't think they are as broad as you are suggesting.
You can't use Google's fully-trained models as a reference in order to train your own models. Lower-level uses of TPUs to train your own models from your own training data are unrelated to those restrictions.
Certainly nothing in the Acceptable Use Policy looks anti-competitive to me.
So is the only reason to buy TPUs to learn about them and go work for Google or something? Why sell them if you can't use them for anything (as Google considers anything computing to be under their domain).