Before transistors were created in 1947 by American physicists John Bardeen and Walter Brattain and vacuum tubes in 1908, electric circuit switching between on and off was a purely physical, mechanical process done via relays (invented in 1809). Some people have made whole computers from relays. But as ElectroBOOM comedically describes, there are a lot of difficult problems that relays had to be overcome which leads to an amazing number of trade-offs of speed, heat, longevity, safety, etc.
While we consider flipping circuits on/off in the GHz range (1,000,000,000 times per second) common on today’s modern transistor-based circuits, many of the same problems he describes here exist in some form in transistors (switching time, etc). Instead of the more mechanical issues/solutions relays use, transistors solve related problems with the types of substraits, power properties, etc.
At any rate, it’s a great trip back in time and a reminder that engineers know that while a concept looks very simple on paper, the devil is in the details – and sometimes those devils take decades to work out (if ever).