You already answered your own question. A 2 stroke engine running at 10,000 RPM has 10,000 combustion sequences. A 4 stroke engine would have only 5,000 combustion sequences. The 2 stroke is burning fuel at a faster rate and producing more power than an equivalent displacement 4 stroke.

Also, the 4 stroke has more moving parts and has more friction loss.

A rather simplistic answer but basically that is the difference in power between the two.