Strange. Just can’t get my head around it either. Cannot imagine them missing something so serious or not being able to pull out of the dive. Regardless of stabilizer position, the B737 still has manual reversion and enough force should have gotten them out of a dive.
As said above, the trick is to find out why they went from close to 15-20 deg nose up to nose down. All I can think of is that now that the Windshear warning was gone they were trying to get back to a clean configuration.
In context I guess when they departed they had the following:
APS 42.5T
Traffic Load 5.5T
Take-off Fuel: 20.0T
TOW 68.0T
Burn to 1st App 9.5T
First approach 58.5T
Further 2.5h hold 6.5T
2nd Approach 52.0T
Vref 30 at 52T is approx. 132 kts
Limit speeds:
F1: 250
F5: 250
F10: 210
F15: 200
F25: 190
F30: 175
F40: 162
So it looks like they would have still had a 40 margin for flap overspeed during the initial go around. When the windshear warning stopped they would have selected flaps 15 and gear up. Followed by flap retraction in accordance with the bug. Looks like it never got to that.