The freelancers can just write under their own names. Mathematically, people who can create substantial value by creating high-end content who are also CEOs must logically be a subset of the total population of folks who can create valuable high-end content. So you would expect at least some market for high-end content creation, but nothing like that actually exists.
Right now there are a handful of individuals who have landed one-off gigs doing this, but there isn't any sort of marketplace.
There is. It mostly exists in the form of subscription newsletters and paid research reports of various types. Specific examples include subscriptions to IT industry analysts such as Gartner. (Typically subscriptions include personalized services in addition to reports.)
In general, this has become a much tougher gig outside of a handful of large firms--because of all the competition with free content.
But that doesn't mean that this can be replicated by just having a freelancer pretend to be writing as the CEO. (Though PR folks, editors, etc. help with such projects.) And even when books are largely ghost written for celebrities and such, the ghost writer is still just going to collect a fairly modest word rate.