Why miners solve a puzzle in proof of work
No, the time spent creating a block is tiny and even a simple cell phone could make it in a few microseconds, if we leave aside the puzzle-solving time.

The purpose of mining is not to find who has the most computational power, but to make those miners with lots of computational power to 'waste' electricity. I say 'waste' but it's not actually wasted because mining itself is important. I mean in the sense that, to create an artificially scarce resource - bitcoin - mining was designed to take advantage of naturally scarce resources: electricity and computer time.