As other have said due to the overhyping (poor volta) and the obvious powergames he was playing (RTG) made him very unlikable.
What makes him unlikeable to me is his pathological self-promotion. Besides being an annoying quality in and of itself, combined with his extremely poor track record heading RTG it makes me seriously question his ability. Did he climb the corporate ladder because he's competent, or is he just good at playing the corporate game? The same traits that helped Raja gain his limited celebrity are also the traits that would help a rung-climbing career-minded corporate sociopath attain a powerful position.
Under Raja's leadership it's not just that RTG took a swing and a miss ala. R600 or FX. They both failed to properly innovate on GCN while simultaneously falling on their faces whenever they did try anything novel (eg. primitive shaders). Sure, AMD doesn't have the resources that Nvidia does, and AMD was more focused on CPUs but, honest to God question, if you could go back in time and replace Raja with Keller (or the GPU equivalent), and
then cut the already limited GPU budget in half do you think you would end up with a better performing RTG or a worse one?
Even without pointing out how R&D giants like Intel can flounder while plucky startups sometimes make magic, I think we all instinctively know the answer to that one. You do good engineering by having good engineers and good leadership.
Occam's razor here says that the only thing Raja is especially skilled at is promoting Raja.