Well, there is at least another source with better visualizations AND explanations of bezier curves. So I'm not impressed at all.
The ultimate guide for bezier curves including great animations to explain the concept is from pomax:
http://pomax.github.io/bezierinfo/
I would go as far as to call it a bezier reference document. I learned both geomteric and numerical approaches to calculate, combine and draw bezier curves from this source. I am still amazed by the beauty of de Casteljau's algorithm.
The document has been submitted here before:
https://news.ycombinator.com/item?id=8804691