Dubas never signed "unprecedented dramatic overpayments". Dubas signed contracts based on the cap at time of signing that were consistent with the history of post-ELC contracts.
It's a trade-off. You sign for what is likely to be a little less in overall dollars, in order to lock in financial security, and take away the risk of a downturn in the 3rd year. Unfortunately, with Babcock abusing our young stars and holding them back offensively, there was likely less incentive for our players to want to sign early.
You're discussing two different things. Players are signed based on the cap at time of signing. Both Crosby and our RFAs did this. Throughout the history of the cap, the cap rises, and that percentage of the cap decreases over the life of the contract. Unfortunately, due to the unforeseen global pandemic creating a multi-year stagnant cap, the Leafs did not experience this lessening of the cap hit percentage for their players like every prior team did throughout the cap era with their players and contracts - making things unexpectedly tighter.