Charlie Casserly was the proverbial "kick me" sign that other owners had planted on Bob McNair. The owners knew what Casserly was and knew that the Texans would be an easy "W" for the years that he was the GM. And they were right.
David Carr, on the other hand, was pure owner hubris. He never had to compete for the job and was gifted the starting role just by being drafted at 1.1, and by looking good on inaugural season merch.
Notice that neither Casserly nor Carr found any success in the NFL after their stints with the Texans, and both ended up as "analysts" on NFLN in the end. Which really reveals the low standards that NFLN has for analysts, because both of them are babblers that never offer much true insight into the NFL (or football in general, tbh).
Fortunately, Kubiak arrived and eventually achieved the franchise's first winning season, first playoff berth, and first playoff win. For a while I was worried that this franchise would be like the Saints in never having a winning record for the first two decades.
Now I just accept that this franchise will never reach an AFC championship game, much less a SB berth. It is what it is.