Why did Dick Clark move his American Bandstand from Philadelphia, Pennsylvania, to Los Angeles, California? Specifically, what prompted him to do that?

Clark admitted to accepting a fur stole and expensive jewelry from a record company president. He was admonished for only this single transgression, despite the fact that songs and artists that he held considerable financial interests were frequently feature on American Bandstand.

At the end of the investigation the Senators could find nothing illegal. In mid October, 1959 ABC-TV told Clark to give up these outside businesses or leave the network. Clark sold those interests

Clark moved his headquarters to Los Angeles in the 1960s. In 1965 he produced "Where The Action Is" for ABC-TV. Hosted by Paul Revere and the Raiders it was a "Bandstand" type show. Clark continued to host American Bandstand after it left ABC-TV and went into syndication. When he quit hosting in 1989 it had become the longest running television variety show of all time.
http://www.history-of-rock.com/clark.htm

In 1964, Clark moved the production of American Bandstand to California, cutting broadcasts to once a week. In part, the move was made to facilitate Clark's expansion into other program production. Additionally, it became easier to tap into the American recording industry, the center of which had shifted to Los Angeles by that time. The show's popularity with teenagers continued until the late 1960s.

https://interviews.televisionacademy.com/shows/american-bandstand