Railways first appeared in Britain, and 1,435mm gauge appeared early on. Stephenson locomotives had become the standard, and used 1,422 mm gauge railways. This would later be broadened for the hugely successful Stockton and Darlington Railway in 1825 and Liverpool and Manchester Railway in 1830.

After the success of the Liverpool and Manchester Railway, the first intercity line, more and more railway lines appeared on the British isles. During this period 2,140 mm broad gauge started to appear in Britain as well and continued to grow in popularity alongside standard gauge. A rivalry between companies using standard and broad gauge appeared.

When the British began to export their railway technology to other countries however, standard gauge was the norm to export. Other countries started to manufacture their own railways and rolling stock. The gauge used depended on the rolling stock used, if you used British locomotives or based yours on them you build in standard gauge. But if you used say Russian locomotives, you used Russian gauge.

And then we come to the conclusion, that even to this day standard gauge is actually not universal. Only 55% of all railways worldwide use standard gauge, Russia and Spain famously chose not to adopt standard gauge as to disallow invaders from using their trains on captured territory. You're unable to take a direct train from Poland to Lithuania due to the gauge differences, Spain only uses standard gauge for its high-speed trains that connect to France, and the Trans-Mongolian Express needs to stop at the Chinese-Mongolian border to change the bogeys from Russian to standard gauge or vice versa. While standard gauge is the most popular gauge, it's still far from universally used.