I'd say it's durable object specific. Both team deno and cloudflare (and many others) have been won over by the paradigm. Cloudflare is just the primary implementers of it as a strong example of an actor-based programming model at infra layer, but others have been trying to push it (Rivet, and TerseAI's durable actors, celld)

EDIT: like the whole enthusiasm is that they are buying them because they are generalizing a thing to be NOT a cloudflare thing