WordPress also has multiple contributors — it's just mostly under the control of Automattic, just like React is Facebook, TypeScript is Microsoft, and Go is Google.
I think the difference is the latter three had internal projects the OSS'ed them. On the other hand, WordPress was built on the back of a "community." There is a lot of distrust, and rightfully so, from how Automattic put itself first and the WP community a distant third.