Compared to the 1979 Chicago DC-10 crash when it took 12 days for the FAA to ground the DC-10, 3 days is much faster.
If I were a Boeing manager, I'd much rather deal with a temporary grounding than a third crash.
Corporate memory fades over time, engineers with scar tissue retire and MBAs pinch harder on pennies.
The 787 battery wake up call seems to have been treated as a one off without a deeper look into how that design snuck past the DERs.