You prove his point when you mention that there was "no major upgrade the roster". Kerr inherited an elite team that didn't have to play anyone in the playoffs (a depleted Pelicans, depleted Cavs, and a washed D12). Jackson got them to beat stacked teams in their own buildings (the Miami Heat's big 3), prompting people to call them "stacked" (Splash Brothers and at the time Lee, which most saw as a Big 3), "contenders" (because of solid defense), etc, repeatedly (titles they had never been given) because they were playing elite basketball on both ends (I can post quotes too; they got these titles under Jackson). Mark is largely responsible for the contracts Klay and Draymond got and the 1 Curry will get, getting people to place a lot of expectations on them, turning Curry, Klay, and Draymond into All-Stars, etc. Klay couldn't even play defense before Jackson. He developed them so well, that literally 2 rookie coaches (Kerr and Walton) were able to have a lot of success with them.