That's not quite accurate. Sussman says that the more fundamental computer science that he and Abelson had taught up to 1997 or so had become obsolete, because the transistors had disappeared into massive chips and the code had disappeared into libraries. Software and hardware became a matter of integration.

He told the MIT people in charge of developing courses that he and Abelson were quitting, and they should figure out what to do next. The world had moved on to interfacing complex chips to sensors and actuators, and it wasn't easy, because the chips were imperfectly specified. To a certain degree, you tried different things to see what worked. I think he was rather disgusted with the situation, compared to the clarity he had a couple of decades earlier using Scheme.

So, the MIT professors that replaced him went with Python. It had great libraries, and it was amenable to fast turn-around when gluing software and hardware together in the lab.

I had a discussion with Sussman a decade or so ago about this, and what he told me then agrees with what he says in the video.