Yeah, there's that angle, too.Never attribute to stupidity that which can be attributed to human malice.
Their thoughts are more like "if I cut these corners, I will show a 60% profit increase which will translate into me getting an X million dollar bonus. Then I retire on a golden parachute just before shit hits the fan. Sure the company will fail soon after... but what do I care, I got mine... if I am really lucky I can even switch to another company just in time and suck it dry too".
For them failure is when the company explodes before they retire, or when the company does not die just after they retire (showing they could have sucked more out of it, but were too conservative).
Occasionally such failure occurs, other times them manage to maximize the amount of blood they suck out of the company before it dies.
To be honest instead of bean counters it would be more accurate to call them vampires.
... although there is this myth about vampires counting grains due to extreme OCD. So beancounter can be a perfectly viable shorthand for [bean counting math vampire]
Suck them dry, jump ship, suck them dry, repeat. And worse still, these people always get hired on at top-level or prominent roles, like bank CEOs.