eBike technology explained

Hey everyone!

I've been diving deeper into the world of eBike tech lately, especially as I'm thinking about upgrading my current commuter eMTB's motor or even building a custom battery pack. It got me wondering, what's one piece of eBike technology that you found surprisingly complex or surprisingly simple once you understood it? For me, understanding the nuances of different motor controllers and their impact on torque vs. speed has been a real rabbit hole. What's been your biggest "aha!" moment or a tech detail you'd love to see explained better for DIYers?