What is the rationale for exponent and mantissa sizes in IEEE floating point standards?

Question

I have a decent understanding of how floating point works, but I want to know how the specific exponent and mantissa sizes were decided upon. Are they optimal in some way? H

Answer 1

According to this interview with Will Kahan, they were based on the VAX F and G formats of the era.

Of course that doesn't answer the question of how those formats were chosen...