As has been pointed out many times in the two main threads discussing the 737 MAX crashes, the LT610 PF counteracted uncommanded (MCAS) nose-down trim on 21 separate occasions, yet for whatever reason did not believe he was experiencing a stab trim runaway, and failed to activate the CUTOUT switches.
There are two big questions:
- why did he fail to recognize the stab trim runaway and activate the CUTOUT ?
- why did he hand control of the trim to the FO with such a critical malfunction occurring ?
Good questions, but as I said much much earlier, I think we can turn this one on its head and ask "what enabled the supernumerary Captain on the prior flight to recognise, at least in part, that CUTOUT was the solution?". I believe that, even then, electric trim was re-engaged albeit briefly.
So, even with 3 heads in the cockpit, one of whom was free from immediate control issues, it did not appear to that crew the Trim Runaway NNC was the obvious choice.