alt Hacker NewsGWT was a huge success, and eventually became obsolete -- which is not the same as "failing horribly".
It took a long time for the web ecosystem to build up the capabilities that removed the need for GWT.
For a while, it was quite a good way to build and heavily optimize certain kinds of web client applications.
Yeah, I believe some ex-Googlers even claimed that writing Gmail was simply impossible at that time with ordinary JS, and the abstraction behind GWT was an absolute necessity (though maybe the frontend part was not all that important - closure compiler is still alive though)