Reasonable size lumen package (small enough to not be that of a problem to design with, large enough that the production costs were not that high) combined with reasonable size (fit for standard ceiling patterns) and good system efficiency made them favorites of mainly commercial applications, where the total cost of the light was the top priority. The high demand from commercial sector made the production volume to ramp up. And large production volumes led to lower costs because of economy of scale and brought more RD money to get even better performance from their systems. And lower costs made them even more favored.
Until the F40T12 became the virtually only workhorse of industrial lighting.
The F32T8 is then "just" a more efficient replacement, even when it meant a need for different ballasts (the OCV of the then most common RS ballasts was not enough to reliably start the F32, so a new ballast was needed anyway, so the spec evolved to maintain the lumen equivalency), the equivalent lumen output meant they perfectly fit into older systems (with just the ballast replacement).
In Europe then common glowbottle preheat start systems were able to ignite the T8 perfectly fine, so the evolution went to make the F36T8 electrically compatible with the F40T12 ballasts, with the assumption part of the lamp positions will be skipped to get the desired power saving from the system.
