Why Newton’s laws of motion explain correctly the earth’s orbit but not mercury’s?
Where Mercury is concerned, Newtons formulation succeeded on one level and failed on another. Newtons formulation implied that there was a more oblate inner sun. A flatter inner sun means a faster spinning oceanic sun. Faster spinning and more dense. But Newtons formulation failed in terms of its projection of the relative mass of the sun. The formulae suggested that the sun was not particularly dense overall and so must have been made mostly of hydrogen.
The hydrogen sun thesis was a grave error. Since it lead to the fantasy of hydrogen self-compression. The problem is that we were probably still six decades or more away from being able to collect the necessary data to do a second draft on Newton’s good works at the turn of the century.
Its not so much that the situation was ripe for opportunistic abuse. Because what team Einstein got going went way beyond mere opportunism. It would be good if Einstein could simply be forgotten so we could get on with it. But we are not talking about yesterdays scandal.
So anyway Newtons setup did not do too badly. 50/50 with regards to Mercury. There is an inner water ocean. But the sun is not made of hydrogen.