I am a pro artist and you have it exactly. There are many, many decisions along the way from a rough sketch to a finished work, and making them is a lot of the fun. Part of making these decisions is also turning a lot of your brain off while you draw, and vaguely thinking about where to go once you finish what you've done so far.

Serendipity's part of it too, like I could see the "waterfall teapot" starting with just idly modeling a teapot with no particular goal in mind, then accidentally stretching the mouth too wide, laughing at the result, and deciding to experiment with a bunch of absurdly-wide teapots until arriving at the final result.