You obviously aren't all ears, because I already told you. Kadri has been a Leafs his entire career. He has played all of his playoff games prior to this year with the Leafs. He had not been very good at all in the playoffs. Using his amazing run with Colorado this year to suggest that he'd do that with the Leafs is silly, because he has been with the Leafs for a very long time and did no produce anywhere near that much. Following still?
Tavares is a much better player than Kadri. $6.5-mill better? No, of course not, but I'd certainly rather have him in the #2 slot than Kadri. What D-man should the Leafs have signed with the money between Kadri/Tavares? Who has been available that would be worth a massive downgrade at center (and yes, the difference is significant)? Should the Leafs have not signed a #1 center for the sole reason that 3 or 4 years down the line Pietroangelo might hit UFA and might choose the Leafs? Tavares' contract isn't the Leafs issue. Its the crazy Marner contract that really holds them back, IMO.
Side note, LD is the one of the Leafs strongest positions (Rielly/Muzzin/Dermott/Sandin), so they wouldn't be looking for a #1 LD.