Yes. But in reality it was more "write once, debug everywhere". It was actually quite a nice concept, but the resulting UIs were inevitably clumsy and had that distinctive (ugly to me) look, no matter what the platform promised. If it doesn't look good out of the box, it won't look good later either.
People wrote Java applets that were supposed to be same everywhere. It even had GUI.
Nobody expected that not Java, but _JavaScript_ will be the actual write once-run everywhere.