I think Toronto's biggest faux pas was thinking they could fit both Tavares and Nylander under the cap without compromising the bottom 6 or D in the short and long terms. They've got Matthews, Marner, Tavares and Nylander on huge contracts without any of them having had serious success at the NHL level, beyond personal accolades. There will be so few teams interested in taking on a contract of Marner or Nylander's size that I can't see either being traded for close to fair value. And without trading one of them, it's hard to imagine Toronto being a legit contender without a serious cap rise.
Colombus is an underpowered team, where even their best players not named-Jones (Dubois, Werenski, both goaltenders) would be considered second-tier on most competitive teams. But they have grit, determination and a stubbornness you can't manufacture. They're perpetual underdogs, they know it, and my God do they work hard to try to overcome it. It shouldn't be a surprise that the last two Cup winners - Blues and Caps - won after overcoming some level of regular season adversity that made themselves, and everyone else, doubt their chances. Toronto doesn't seem to have acquired that kind of doubt, like Tampa last year, and that costs them time and time again.