It would be a failure on SRB's part to see Virgin Atlantic taken apart. He has to actively want to sell out and after the failure of Virgin Galactic, I doubt he'd want the publicity of pluckly lil VS fighting BA giving way to tiny little VS eaten by American giant.
Looking at it from the outside with no axe to grind, it does appear to be the case that efforts were on concentrated on an unwinnable war against BA rather than on the development and profitability of VS.
First law of common sense? Don't fight battles that can't be won. There's no point.
Also, had allegedly puerile personality clashes been put to one side, maybe there could have been a deal/collaboration between BD and VS all those years ago, and both might still be thriving carriers.
Let's face it, their route networks perfectly complimented eachother, and this would have been the way to give BA a "run for its money" at LHR.