I have no facts. What I think is that Chevy fell down on the job, maybe due to the bankruptcy in 2008/9. Ford was already dominant in the C's, and they just took or got all the market. I have no idea how hard Chevy is working now to get back in. I know I bought my Sunseeker on a Chevy for the same reasons as you mentioned. They are on some smaller C's today, but no bigger ones that I know of.
You know the RV industry, they don't seem to want to mess with change unless they get dragged into it. They are geared up now to build on Fords. All just IMO.