That’s pretty much only because of Hollywood’s film industry. It isn’t comparable otherwise.

The greater LA area has Hollywood film and television and a lot of music stuff too. It has the 16th and 19th busiest container ports in the world (Los Angeles and Long Beach) [1]. It has the 11th busiest airport by passenger volume [2], and several other airports because that one isn't enough for the area. It has a pretty extensive computer industry. There's a lot of petroleum processing. There's a lot of agriculture. There's some financial services (many cities in the US are bigger in finance, but there's still a lot in the LA area). A pretty good amount of manufacturing. Several top tier universities. It drives a lot of tourism.

And then there's all the GDP that arises from the population itself: construction, healthcare, education, real estate.

If you take away the entertainment industry, it becomes a different place, but there's a lot of economic activity and most of it isn't film and tv and music production.

[1] https://en.wikipedia.org/wiki/List_of_busiest_container_port...

[2] https://en.wikipedia.org/wiki/List_of_busiest_airports_by_pa...