The 737 MAX is in part unstable due to repositioned engines. They are larger and thus significantly more fuel efficient, however they would not keep enough ground clearance if they were positioned the same way as on the 737-NG. MCAS corrects for the repositioning, otherwise the plane may start to climb which in turn could lead to a stall.
How does B follow from A? That's quite the non-sequitur.
Reductions in fuel consumption factor greatly into ticket prices. It's easy to reduce services (luggage, refreshments, leg space) but reducing fuel consumption is entirely up to the aircraft manufacturers.
This is an example of a tragedy of the commons. Market forces found a solution to a problem (for one actor) that externalized long term costs for the sake of sealing a short-term deal, that in the end, was not guaranteed to stick around.
In fact, I am very much against low costs flights like that and would rather see less planes in the air, as long as they burn fossil fuels.