My guess would be that it parallels other backend software revolutions.

Initially, first party proprietary solutions are in front.

Then, as the second-party ecosystem matures, they build on highest-performance proprietary solutions.

Then, as second parties monetize, they begin switching to OSS/commodity solutions to lower COGS. And with wider use, these begin to outcompete proprietary solutions on ergonomics and stability (even if not absolute performance).

While Anthropic and OpenAi are incinerating money, why not build on their platforms? As soon as they stop, scales tilt towards an apache/nginx type commoditized backend.