Shanahan never should have had so much say over hockey ops. The dude had 0 GM experience, just worked in the NHL office and was in charge of discipline for a while. Being hired straight away to be the guy over the GM made no sense. If you're going to do the dual heads thing, you need an experienced GM leading a younger one.
Treliving had least has 20 years of experience an an AGM and then GM. Makes no sense to have a guy like that be under the supervision of a guy who prior to joining the Leafs had never even been an AGM.