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Anyone care to speculate based on physics why this might have worked out this way?

Indulge my wild guess (I'm not a physicist):

If the proto solar system's matter distribution was a Gaussian-like distribution, it would make sense that matter density droped in a logarithmic scale, and thus planets formed droped logarithmically w.r.t radius.

More intuitively.. further away from the sun has less probability for rocks/particles to interact with each other.

In our solar system, the small planets are closest to the sun.

Jupiter, with 72% of all planetary mass, is more than twice as heavy as all other planets, combined.

Saturn, Uranus and Neptune take most of the remaining 28% (https://en.wikipedia.org/wiki/List_of_Solar_System_objects_b...)

(Of course, there also is way more volume that far away)

Another wild guess: a sphere of gas collapsed to a rotating disk. If you take a sphere and squash it flat, the middle has most of the mass, and it declines to zero as you get farther. I would guess the pattern of falloff of a squashed sphere is roughly logarithmic. That pattern gets quantized into planets, and so we see the original spherical distribution in our planets.

That makes a lot of sense.

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