I suspect they had a certain number of miles they wanted VB to be from WDW. It is very reasonable for a family staying at VB for a week to take a day trip (or two) over to Disney World and visit a park.
I think the Florida Coast options were also limited generally. Do you go upscale with a Disney resort in Naples? Or do you associate Disney with Daytona? So, I think they decided to make it more about the Beach, and a serene setting.
And, for a timeshare, Disney did a good job with VB of trying to make it a resort - a full service restaurant open for two meals a day, a pool bar, and a quick service restaurant, lots of activities and amenities, a strong presence with activities teams, movies on the lawn, Campfire at night, etc. A second pool, originally planned, would have also helped, as would have a larger resort (also originally planned) that would have likely included additional amenities.
Nevertheless, the concept was not what people were looking for. I suspect one of the obstacles they had with selling VB was people saying "where is that exactly?".
My understanding is that HHI had no real issues with selling the first time because - people knew where HHI was, and it is a very small resort.