Read the letter again. This CEO is absolutely
not forthright about taking the blame. He doesn't even speculate about root causes, much less assign blame. He describes the problem...
"While our revenue has grown by five times since the start of the pandemic, our costs have grown by even more as we geared up for a continued rate of growth that now looks unlikely. Additionally, so much of our organization was built for a paradigm of rapid growth, in terms of the roles, ratios, and structures we’ve put in place."
...but nowhere does he talk about why these things happened.
He literally uses the passive voice top avoid taking responsibility ("our organization was built" not "I built").
You come away with the feeling this is a good letter in which he takes responsibility because he distracts you by spending the rest of the letter describing the details of the severance offer, which is completely orthogonal to the issue of root causes and responsibility.