I think it's more productive to analyze the adoption (or not) of a technology from the perspective of it being a cult, rather than with strict technical factors. A cult grows as an emergent phenomenon where the conditions on the ground create incentives for new members to join faster than old ones leave.

Through this lens there are actually two cults with two cult rallying cries:

1. The browser is, arguably, a terrible program execution environment. You have to use a stupid language and there's a ton of pretty standard things you can't do (e.g. have proper concurrency). Let's fix that by baking a proper program execution environment into the browser.

2. There are lots of places where someone builds an application (a real application that runs as a process on an OS) that then needs to support some sort of embedded programmability. Historically there have been many ways to do this: embed Lua, embed a Python interpreter, embed a JS interpreter, write the application in a language that inherently supports runtime dynamic binding (Java, Lisp, ...). Let's make a better version of that thing such that it supports all common languages.

My take is that while WASM was developed by people in the #1 cult, it has actually been adopted by people in the #2 cult. I see WASM used all over the place as a way to host user-provided code inside things. Blockchain nodes are a common use case, for example.

Then there's a third use case that I think motivates many of the comments here which is: back in the day we could make an application and distribute it to users who would run it on their computers. That pretty much isn't possible now for various reasons, but primarily because computers are locked down (particularly mobile). If only we could be allowed to run regular code inside the one execution environment that's not locked down (the browser), imagine what we could do then. Problem is that WASM doesn't have all the features necessary for this use case. Experience in the past with similar things (ActiveX, Java, ...) suggests that if it did, it would also become locked down.