Look at the X axis labels again.

The chart is trending down by January 2020, changes directions (upwards) right around the March 2020 spot, and again around (down) the July 2023 spot.

The fact that they only have data going back to 2018 means it's hard to say if the pre-COVID stuff was the norm or unusual.

To be super-clear, here's the chart annotated to show that 90 day window (black rectangle) in which the cameras were installed. https://imgur.com/a/i00Gna0

"that drop is obviously in early 2020", to reemphasize, is several years before the cameras got installed.