I learned about the Schwebebahn from this[1] YT video (from The Tim Traveller), which goes into the history of why it made sense to build a suspended rail at this particular place and time. A more recent video [2] gives a much more detailed history.

[1] https://www.youtube.com/watch?v=9IFh6wFTJiQ

[2] https://www.youtube.com/watch?v=sI5DehAuT2I