Of course, there's no way to verify this, but it's an interesting tale. FUD Zilla heard that AMD's management saw much greater value in EPYC than in Vega, as a return to competitiveness in the server market was seen as a priority to safeguard AMD's future:
Taking key talents from GPU and moving them to the server business meant that EPYC has some impressive power to performance ratios but at the same time Vega didn’t. Our well informed sources didn’t want to reveal the names but there are not that many power optimization magicians working in these chip companies, it comes down to a few people. A great leader with a decent team can do a great job.The result is that Vega ended up with high thermals and failed to hit its performance targets, because the Radeon Technologies Group did not have the resources it needed to make the GPU more competitive.