Because Java was doing nothing similar, a better comparison would be .NET CLR that actually tried to be a decent compilation target.

Also security, Java has reflection so you cannot reliably sandbox java libraries

My main one is that WASI has benefitted from an additional 31 years of accumulated industry-wide experience compared to when Java was first released.

Programs written in Java require installation of a middleware called Java runtime. It adds extra friction for end-users. And even if one has Java runtime installed, a newer version may be necessary for a recently-published application.

With WASM it may be the same, unless al major OS vendors integrate a WASM runtime so that it doesn't need to be installed separately.

My main one is: distribution & access. If major browsers implement the WASI runtime then using and distributing a WASI app will be way simpler than the Java equivalent ever was.