The document is actually very interesting, it goes into great detail of exactly how they tracked him. There is so much evidence in it, really a good read. They ended up tracking him with a GPS tracker to prove he set the fire they charged him with.

> Forest Service agents also measured and recorded data about the tire tread pattern left by Maynard's car — evidence that they say ties him to a string of arson wildfires.

That's linking his car to the fire. That's from the article, I'm sure the affidavit itself has more.

The article points out that the person who first spotted the smoke also saw the man walking back from the location of the starting of the fire, about 10 minutes after it started.

Now that they have a warrant and can track his movements, he is coincident with several other fire origins.

No, just read it. That incident had nearby suspicious fire remants. Combined with his unusual behavior and similar car tracks being found at another fire was their basis for further tracking of the alleged arsonist.

Reading the above comment, this was the necessary point to pull his cell phone info, not link him to "all" fires; after such a suspicious interaction, the warrant was granted to pull records, and the case strengthened further.