In December 1968 Engelbart sat on a stage in San Francisco and, for ninety minutes, showed a mouse, windows, hypertext links, shared editing and live video calls with a colleague miles away. People call it "the mother of all demos" and it isn't an exaggeration.
What gets lost is why he did it. He wasn't trying to make computers easier. He wanted to make groups of people smarter, to "augment human intellect", because he thought the world's problems were getting harder faster than we were getting better at solving them.
His lab fell apart in the 70s and much of the industry took his interface ideas while ignoring the bigger point. He spent the rest of his life a bit frustrated by that.