Martinsville falloff through the years

There’s been quite a bit of discussion about the universally panned, utterly uneventful 2022 spring Martinsville Cup race, particularly about the tires. Check out the below links to the lap time graphs of the POMS leaders from the last three years’ spring Martinsville races:

2022 William Byron: starts at 94 mph, down to 93 after 30 laps, 91 after 50, 90 after ~100
2021 Denny Hamlin: 93 to 88 after 30 and holds
2020 Joey Logano (caveat - this race happened in June because of the pandemic): similar to Hamlin; 93 to 88 after 30 and holds

The differences in absolute numbers are minute, but the shapes of the charts tell a pretty clear story of rapid tire falloff in previous years and linear falloff in this year’s race.

I don’t see the same differences in other flat-ish short tracks. You can check for yourself:

Richmond: 2022, 2021
Phoenix: 2022, 2021, 2020

Was it the NextGen car? Reduced horse power? New tires? Cold temperatures? It’s not clear, but there’s something going on.