We have to assume that he was some sort of time traveler.

His "Mother of all Demos" in 1968 included most of the fundamentals of modern human-computer interaction (minus touch screens and voice commands.)

He pioneered the idea of using a mouse to to navigate a graphical user interface with windows that first Apple and later Microsoft adapted as the standard.

He came up with the basic for things like hypertext links and video conferencing and how to mange multiple people editing a single document at the same time.

If you today use things like Office with stuff like teams and sharepoint or any of its competitors that may not sound like much, because that is just the waxy things are done.

they were not as obvious in the 60s. He came up with the whole package while working for Xerox who didn't know what to do with it and it wasn't until Apple started implementing some of the ideas that the world took notice.

phrases like "ahead of his time" and "visionary" get thrown around far too much nowadays, but we didn't catch up with the future he saw until the mid 90s and didn't fully implement his ideas until dot-com bubble burst. It is only now that we try to reach beyond what he came up with and come up with new things many of which fail.