The pilots on lion 610 were in regular contact with ATC and as late as 20 seconds before impact with the ocean they indicated their preferred flight level. This suggests they were not under duress in operating the aircraft until the very end. It is still very much unclear why their successful and consistent NU trim corrections are suddenly insufficient to counteract MCAS.
My understanding is there was a change in which pilot was flying. The first pilot dealt pretty consistently with NU trim corrections. Each ~10 sec ND trim is countered with ~10 sec of NU trim. After the pilot flying change the NU commands were very small, probably less than a second at a time.
So the question is, why the change in which pilot was flying? CVR will go a long ways in helping figure this out if it can be found