The way I look at it is this:
KC had the best chance to be #1 then Buffalo, then Cincy.
Cincy had the best chance to be #3, then Buffalo, then the Chiefs.
Now KC still has the best chance, then Buffalo and Cincy is locked into #3 which they were not before.
You can argue about who got the worse end of this but it doesn't fundamentally change how each team was positioned before the Bills/Cincy game. Bettors would have been putting their money on the Chiefs to get the #1 seed and for Cincy to get the #3 seed.
So we've been going on about how the Chiefs had 50% chance tu get the one seed, but that was just one number from a site that doesn't actually use metrics in their game predictions. This site actually had the probability of the Bengals beating the Bills at around 55-60%. Advanced metrics sites and Vegas had the Bills slightly favored. We also know from the same site I used that if the Bills-Bengals game was decided by a coin flip, than the #1 seed odds were also 47-47-6 (KC-BUF-CIN). So it stands to reason that the
Bills may have been slightly favored for the one seed with more in depth game simulation, since both Vegas, FPI, and other such metrics had them slightly favored in the Bengals game.
TL;DR version: No, is not clear at all that KC was more likely to gain the 1 seed than Buffalo. It was pretty much a coin flip before the game was canceled.
EDIT: Football outsiders, which DOES use metrics when simulating future games, had Buffalo a slight favorite (44%-43%) for the one seed entering MNF. So let's drop this "KC was a clear favorite for the 1 seed" nonsense. The 50-43 edge doesn't say that (that's a "slight edge" at best), and better sites that use more sophisticated algorithms
certainly don't say that. It was a coin flip.