No, it transitioned it to others after signaling it would for well over a year, so i don't think you could call it sudden:
"In 2011 with the introduction of the Dart programming language, Google stated that GWT would continue to be supported for the foreseeable future while also hinting at a possible rapprochement between the two Google approaches to structured web programming. However, they also mentioned that several of the engineers previously working on GWT are now working on Dart.[6]
In 2012 at their annual I/O conference, Google announced that GWT would be transformed from a Google project to a fully open-sourced project.[7]
In July 2013, Google posted on its GWT blog that the transformation to an open-source project was completed.[8]"
Google funded/helped for some number of years after that.
It still is going, afaik, with gwt 2.11 being released in january, 2024.
