It may be that it was time for the hardware that was previously running Arxiv to be retired and this is just another Capex -> Opex decision being made by so many tech companies.

I'd like to know if GCP is covering part of the bill? Or will Cornell be paying all of it? The new architecture smells of "[GCP] will pay/credit all of these new services if you agree to let one of our architects work with you". If GCP is helping, stay tuned for a blog post from google some time around the completion of the migration with a title like "Reaffirming our commitment to science" or something similarly self affirming.