Well firstly we don't actually have the full info in the public domain yet and will presumably have to wait to the end of the standstill period.
Secondly why is it a monumental balls-up First have presented a business proposition to run the SWT franchise, and the DFT have accepted that proposition as the best option, the fact that it may not include some new trains ordered by the franchise or the only recently extensively rebuilt 458's is frankly irrelevant.
Yes from a PR perspective it may not look good and it will interesting to see any First and DFT spin on this and what happens to these trains in the longer term, but then the same applies to Anglia franchise to some degree getting rid of relatively young 379 and 360's, but there are currently plenty of manufacturers who can churn out bog standard short to medium distance EMU's so if they can get a good deal on substancial or complete fleet replacement rather than just replacing the older units alone it probably makes a lot of sense from the TOC's perspective.