Question

why did Einstein develop his ideas in secret

Answer 1

Hey
Nice question...
The theory of relativity didnt came all at a sudden neither it is a mystery.

If u take the flow of science to Developement of relativity, the fact gets unveiled. It is nevertheless an interesting story.

The first Step towards relativity was the Maxwell’s presiction that the speed of light wave or radio waves should be constant. This prediction was not provable due Newtonian absolute space. So he considered Ether as a pseudo medium of propagation.
these predictions were later proved to be true by the Michelson Morley experiment and there was now no need of ether to be considered.
Then there was Lorentz whose transformations are used in relativity, tried to make a theoretical proof for Michelson Morley experiment but failed.
The aftermath of all this work was the special theoey of relativity. Whose first assumption was Maxwell’s prediction and Michelson Morley’s result i.e. the speed of light is constant regardless of position and speed of observer.
Hope this helps you..