Prius Hybrid Drivetrain - How does it work?

Amazing, it’s so complicated, I can’t understand it

 

Indeed , numerous concepts are presented all in one shot, making it very difficult to understand it.
MG1 and ICE interraction as an e-CVT is one of them , also the task of the planetary gear set in the HSD system is a big chunk to swallow.
To shed some light you should look at P610 or P410 transaxle deep dive .

 

The Weber Auto videos are much better, in my opinion. For instance:

However, this video has merit to see a 'cutaway' of everything together.

 

Yeah, I think I am lukewarm on this one.

The most neat-o thing about it was the idea of building a demonstrator out of an actual cut-away transaxle with some little motors to make the parts go around. But the big takeaway seems to be: that doesn't really add much. Even with the cutaways in the case, the parts of the transaxle where the most interesting stuff happens aren't easy to see, and you're kind of taking the presenter's word for what's going on.

I think you're still likely to gain much better understanding by watching the really good Blender demo by @Niels and by playing with @Ichabod's interactive simulation in your web browser. (It might help if you gently nudge @Ichabod to give it a proper https address, because your modern web browser these days probably protects you from JavaScript on an insecure web site, and won't run the simulation. There was a time when a web hosting service might charge extra for https, but that's largely a thing of the past.)

I also found it funny that the cutaway model has so many little bike chains and motors added to it for spinning the parts around, though that's not so much a critique of this video as of the outfit, ConsuLab, that makes that simulator. The machine's description even says

Three individual motors for ICE, MG1 and MG2.​

I am sure they sell that thing for a pretty penny, and they put a lot of work into building it, and it's surprising they did all that without noticing they only needed two motors, because the PSD fully determines all three motions from any two of them. They could have tucked away two little motors, one turning the ICE and one turning the differential case, and done away with all the distracting bike chains cluttering the main-attraction part.

Also, a danger with such a flashy prop is that it seems to take the pressure off the presenter for good explanations, but it doesn't really. Mr. B doesn't seem to have put much time into learning the physics in any of those driving modes, because it seems enough to show the flashy prop and sort of wing it. That does make the presentation hard to gain much understanding from. It would have helped Mr. B to work with the materials from @Niels and @Ichabod first.

 

There is a 10-page document with simple illustrations here...
John's Stuff - Toyota Prius Education - Power Split Device

 

There is a webpage with simple animations too...
John's Stuff - Toyota Prius - Animations

 

I'd say, at this point, it would be really hard to produce anything doing a better job than Niels and Ichabod have done at making the basic operation understandable.

The next inviting frontier might be to produce something that complements theirs in some way, covers some aspect of the theory that they don't delve into....