My understanding has been that the TPP was about opening China to further outsourcing of white collar work by regularizing IP law on paper (which the Chinese would just ignore of course). This would have allowed more paralegal, contract writing, engineering, and even things like radiology (X-ray and scan interpretation) to be outsourced, further gutting the US middle class and transferring more expertise to China. In other words it would have started the outsourcing of non-physical forms of service work and more lower-level intellectual labor. What would even be left of the US middle class after that?
You're right that it was corporate captured but the original goal was geopolitical.
Edit, cite: https://en.m.wikipedia.org/wiki/Trans-Pacific_Partnership
https://www.bloomberg.com/opinion/articles/2018-10-16/best-b...
All I know is that I'm glad the TPP is dead and I'll be happy if nobody with the last names Clinton or Bush ever sits in the White House again.
I say this as someone who leans more toward the 'woke' side of the present culture wars.