I grew up north of Topanga. We lived there because we couldn't afford Santa Monica. This was back before the movie and rock stars took the area over in a wholesale migration. There had been an enclave called "The Colony" north of Malibu Pier since the silent movie days but it was less expensive to live in most of the rest of the area until the 1970s and 1980s. Back when I lived there there was very little out there in the way on amenities: no super market, no movie theater, no middle school, no high school, no Pepperdine College, etc. Many of the beaches that were later developed into public parks were then privately owned land. Topanga, for example, was acquired for corversion into a park by the State of California from the Los Angeles Athletic Club, which had been leasing lots to the people who had built the houses that used to be there. These leases expired in 1973 and the people who lived there were told to remove their homes or they would be demolished.
When they built the Mayfair Market and Malibu Drugs at the bottom of Malibu Canyon, it was a very big deal. Other conveniences were later added, making living in the area more convenient and attractive. The laws of supply and demand did the rest. I believe the record selling price of a house there, to date, is $75,000,000.00. Everybody I grew up with was eventually forced out of the area by escalating rents/real estate prices/property taxes.