ofc he has bigger achievements than siuhy, don't get me wrong. But he played only in a few top tier events in his whole career, probably only called in a subset of those.
Doesn't make sense to bring in another Aussie if you have a promising young IGL who showed a lot of potential in tier 2-3 ready to go. He knows your system, knows a lot of the players, the coach. It makes way way more sense to try him out at the higher level before getting another semi-decent external solution.