[phire]

With hindsight, we know that retracting the flaps was a bad idea.

But check Boeing's MCAS bulletin, which is the only official information pilots received about MCAS at the time of the flight.

http://www.b737.org.uk/images/aoa-bulletin.jpg

It makes zero mention of flaps. It doesn't recommend avoiding retracting them or trying to land as soon as possible.

Trying to land as fast as possible is typicality a bad idea. Planes which have just taken off are almost always over their maximum landing weight. Even if you ignore that, the extra stress of trying to land as soon as possible could cause the pilots to make more errors.

Procedures for issues on take off are typically focused on continuing to climb to gain as much altitude as possible to give the pilots time and space to assess the problem before dumping fuel and landing. The more altitude you have the more time you have to recover.

And unfortunately, climbing through 5000 feet requires retracting the flaps.

[cmurf]

Check the airspeed at the time they raised flaps. It was right at Vfe, and increasing.

I don't know the most likely consequence of flying with flaps 5 above Vfe. Maybe flaps would (asynchronously) depart the airplane, or induce flutter at a much lower than usual airspeed. Either of those is an extremely high risk of losing the aircraft.