That's assuming the downturn is 100% explained by employees underperforming. It's more likely that market forces outside of these employees control caused the downturn.

The correct wording is “Amazon will do anything they deem necessary to make their shareholders happy, no matter if it’s profitable or not.”

I am convinced they have zero data indicating firing these people will be profitable on the long run, only that short term it is, and that’s all that shareholders are interested in.

I’m a big fan of any measure making stock exchange less volatile, like some form of tax on every transaction, to slow down the machine, make short term investments (speculation) less rewarding. This may help in reducing the appetite of shareholders for such short sighted measures.

Your argument is flawed. Reactionary firing tends to be inefficient, but makes shareholders happy on the short term.

Should a company prioritise shareholder happiness over efficiency is the real question here. Their losses don’t originate from these employees nor initiatives; it originates from market conditions.