When Disney released The Love Bug in late 1968, Herbie became one of the studio’s unlikeliest breakout stars. The movie was a huge hit and most critics actually liked it, which was by no means a given for a Disney gimmick comedy. So it made perfect sense for the studio to hit the gas on additional adventures for the little Volkswagen, even if the adventures themselves made increasingly little sense.
You know a movie’s bad when it kills four people. https://commonplacefacts.com/2015/05/08/how-herbie-goes-bananas-led-to-a-radioactive-disaster/