Mathematics stopped being defined by reality – and started to invent new ones

While this article stipulates how this has been the case since 1930, I'd argue that it's been the case since early 19th century too (tbh, before checking, I thought it was late 19th):

https://en.m.wikipedia.org/wiki/Non-Euclidean_geometry#Disco... :

"Bolyai ends his work (from 1830) by mentioning that it is not possible to decide through mathematical reasoning alone if the geometry of the physical universe is Euclidean or non-Euclidean; this is a task for the physical sciences."