I cannot vouch for causation, but there is a distinct correlation between the deadline by when the separated F&B P&L had to be made self standing and not using any federal funds for it (end of 2020), and the accelerated reduction in F&B staffing level and the fact that one of the largest cost components of F&B service is staff cost.
I suspect that the revenues brought in from Coach passengers according to some calculation did not cover the cost of the extra SA needed to serve people beyond the minimum required for Sleeper passengers.
If those correlated events had a causal connection among them then now that that Sword of Democles has been removed things should improve across the board as all that was dismantled can be rebuilt over a little bit of time. So we shall see.
I suspect that the COVID thing just delayed the recovery from the Mica fiasco by tanking revenues across the board with uncertainty about government support to keep the lights on. But that was its net effect. Even absent COVID we would have cycled down to the bottom until md-2020 and then started recovery with the rescission of the Mica clause.
Now one could ask why Congress and RPA and everyone else sat on their thumbs from 2015 to 2020 before actually acting on trying to fix the problem. It may have had something to do with the past experience with "glidepath to self sufficiency" which sort of went away, and people forgot how hard they had to work to make that happen, and what damage it caused while it was around.