Sir Miles Axelrod was behind the whole thing. He invented Allinol and the microwave camera to make cars break down thus forcing them back to fossil fuels and making him rich. Mater is knighted by the Queen of England as a reward for exposing Axelrod. He returns to Radiator Springs where he is recognized as a hero. Finn and Holly stop by and Holly introduces herself as Mater's girlfriend.
Plot hole: There is no reason for there to be sinks in the bathrooms. The cars may be able to use sinks just as they use toilets, but in the bathrooms they are too small and too inaccessible for any use.
Trivia: The Pizza Planet truck is visible cheering on the right side of the track at the World Grand Prix in Radiator Springs at the end of the movie.(01:37:45)
Answer: They heard him recording the message to Finn and found his words suspicious.