Suggested reading…
Isambard Kingdom Brunel
https://en.wikipedia.org/wiki/Isambard_Kingdom_Brunel#Great_Western_Railway

Brunel gauge was indeed a thing back in the day….and Brunel came up with the idea because a ‘broader gauge was the optimum size for providing both higher speeds[44] and a stable and comfortable ride to passengers. In addition the wider gauge allowed for larger carriages and thus greater freight capacity.[45]