The picture insets are arson arrests, shown on the pattern of recent fires. So it is showing you both, and thus highlighting that the arson arrests are a large subset of the recent fires - and similarly distributed along western highways, near particularly left leaning cities and the highways between them, etc.
sauce
https://www.arcgis.com/apps/PublicInformation/index.html?appid=f8a0d8814a67445a9e6bf3485f4fd24f
EDIT: Also seems this post is an exact copy and paste of a tweet. https://twitter.com/FrznShrew/status/1306656191842586634 https://twitter.com/BrianGPowell/status/1306832614163189762
https://www.reddit.com/r/conspiracy/comments/ix1wjv/arson_arrest_map_pretty_much_destroys_the/
https://centipedenation.com/transmissions/huge-dump-of-articles-and-videos-showing-arsonists-to-blame-for-fires-on-the-west-coast/
Is this just a fire map, or an arson arrest map?
The picture insets are arson arrests, shown on the pattern of recent fires. So it is showing you both, and thus highlighting that the arson arrests are a large subset of the recent fires - and similarly distributed along western highways, near particularly left leaning cities and the highways between them, etc.