That's more of a property of the client side stack rather than inherent of Javascript itself right? If so, do you believe any language could have been in Javasc

That's more of a property of the client side stack rather than inherent of Javascript itself right? If so, do you believe any language could have been in Javascripts spot today as long as it was supported by Netscape client side, even if it were say C++? Also, that doesn't answer the painfully slow adoption of Compile-to-JS languages which would also be written once and run anywhere.