As a strategic move, this makes a lot of sense for Amazon. Moreover, Amazon is a company known for excellence in a diverse set of disciplines, and TSMC has an excellent reputation for delivering state-of-the-art CPUs at scale — yet you are here to doubt they can pull it off, despite providing no evidence or rationale for your position?

The burden of proof is on you to justify your pessimism. If you have evidence for your claim that Amazon + TSMC will have problems scaling, please provide it.