Why don the planets in our solar system orbit the sun in order of their mass?
There are various theories about how the planets formed, and how they acquired their initial velocity and angular momentum. Whichever theory is correct (even the creationist view) one thing is for sure: the planets’ orbits are remarkably stable. Only a very small proportion of their energy and angular momentum is exchanged with other bodies (Neptune and Pluto are a mild exception to this). So the planets simply stay in the relative orbits that they had when they initially settled into stable orbits, as the solar system was taking shape. There is no physical force which should cause the more massive planets to swap places with other planets in order to reach your proposed order by mass. The period of rotation of a planet (which is small compared to the sun) is not a function of its mass, only a function (Kepler’s laws) of the distance from the sun.
