Does anyone even know for sure what the decision to switch was actually
based upon?
Not really, but I have seen Debian rejected at several companies (customers) due to too-short support of old releases and too-far away releases. Both are real problems, regardless of why DreamHost decided to give up on Debian.
-- Pau Garcia i Quiles http://www.elpauer.org (Due to my workload, I may need 10 days to answer)