‘how can it be possible for two professional pilots on a type with a known and highly public failure mode to appear not to be aware of it's symptoms when it occurs to them?’
You appear blinded by hindsight. ??? How on earth do you figure that? But something had them blinded, that's for sure.
The first symptoms and alerts immediately after takeoff were of low speed, approach to stall, erroneous air-data. The crew managed this situation correctly, concluding UAS. They never even started UAS! Had they concluded it the autothrust would have been disconnected, speed/pitch/thrust under control and flying reasonably normally, not trudging through more or less normal after t/o actions with no atempt to deal with anything else, even including engaging a/p at 400' with a stickshaker going????
Note that the alerts and annunciations for UAS are similar, identical to the emergency AD re MCAS except there was no trim activity. Having read the AD, Lionair reports and discussions they'd know to be only anticipating MCAS activity at flap retraction. Events and sequence were all but identical to LionAir. I rest my case! How could crew on a type that had just suffered such a well publicised accident not recognise the similarities?
Subsequently, flap retraction, MCAS moved the trim.Re-read last comment above. How was it not blindingly obvious at this point? Previous discussions have considered the salience of trim activity and time required to conclude a failure in an intermittent system.
The combination of increased stick force - ‘fly the aircraft’, which they didn't do, did they? and UAS could be interpreted as control difficulties - speed error could affect the feel of the aircraft - as would trim. I suspect they never looked at the speed, or they'd have made the connection between full thrust, overspeed etc etc. And the mythical 'completion of UAS' would have ascertainied which speed indications were reliable/in error so that's not a sound answer.
Thus the crew required a step change in their mindset to associate the revised situation with MCAS which ought to have been in the forefront of their mindset , or at least trim problems and then isolate the trim system. Go and re-read that line again! This should all have been complete deja-vue! Inexplicable trim problems four months after the last big accident - how can memories be that short?
Surprise, startle; the original problem understood, now its not ! I don't think they understood much at all I'm afraid.
If a whole bus-load of people in your previously bear-free neighbourhood were eaten by bears a couple of months ago in the scariest event your neighbourhood has ever seen and you were wandering home one night - fat, dumb and happy others might quite reasonably question the appropriateness of your low-key mental state. Is it wise under the circumstances? But even with one's attention being on the path if you sudenly hear unfriendly animal noises right behind you do you really think - oh - that sounds unusually large and fierce for a raccoon but instead of doing the racoon drill all I'll do is carry on as normal and maybe throw it some peanuts- and just carry on strolling eyes-front as the thing bellows away behind you? It never occurs to you to have a suspicion about what's actually growling? And when you hit the moonlight where you know it'll attack if it actually is a bear you still just stroll on oblivious no thoughts of bears in your mind at all? - indeed you begin to run which is going to make it bite all the harder? And even when it's chewing your arm off your'e still saying, "nice Rocky, have another peanut?" instead of pulling out your bear-gun because you didn't read the newspapers or talk to the neighbours who all said that would be a pretty good idea under the circumstances? Didn't the fact you were even carrying a bear gun suggest to you that even with a runawway bear chewing your ass it might just be there for a useful reason?