NFL

1. Lots of players were taking the blame when Vance was under fire, those guys might’ve been more honest than fans took them to be. Poor tackling was a big problem regardless of how open receivers were getting, a big 10 yard catch early in the season became a 20-30 yard gain.
2. We replaced CBs dammarri Mathis and Essang bassey with Jaquan McMillan and Fabian Moreau, cut randy Gregory and frank clark to give our young guys more snaps along with baron browning returning from injury. PJ Locke came back from IR at safety. Mike Purcell back from injury on Dline. Justin Simmons and Josey Jewell (our two players who communicate coverages) came back from injury.
3. Small samples in both directions, we’ve played 4 bad games and 3 good games on defense.
4. Players getting comfortable in the scheme.

The dolphins outlier where players had given up midway through the 3rd definitely skewed their stats. Overall they are probably closer to an average defense considering things didn’t change that much from Evero to Vance.

We benched Damari Mathis

Green Bay sucks.

The Chiefs offense sucks this year. People giving them way too much leeway because of Patrick Mahomes and Travis Kelce name recognition, and every week it's all "they're just ironing out the kinks", but the Chiefs offense, objectively, sucks this year. It took a year longer than we thought it would, but having no replacement for Tyreek Hill has finally bitten them hard. Like, seriously. Can anyone, with a straight face, name a worse starting WR room in the NFL right now? Maybe the Patriots?

So, to answer your question, I'm not sure I'd take Denver's last three games as an indication that their D took a stratospheric leap.