I doubt it would be hard for Microsoft to rebuild, Microsoft Research has made many excellent contributions to transformers for many years now, DeepSpeed is a notable example.
I don’t think they’ve had the will/need to have done this but they most likely already have the talent.
Apparently Microsoft already had plans to spend $50 billion on cloud hardware.
Now they are getting software talent and insider knowledge to replace OpenAI software with in-house tech built by Sam, Greg and others that will join.
Satya just pulled a kill move on OpenAI.