Do note that this idea of technological determinism[0] is referenced directly in the parent article.

As for me, I'd like to think that a bit more nuanced approach is better. Yes, stirrups might enable men to use horses in new ways and to brace themselves on horseback. But this sort of expensive heavily armoured cavalry cannot exists in a vacuum. It needs a class of wealthy people who can buy armour and horses. The wealthy need some sort of motivation to train themselves as warriors and so on. If you are interested in the subject, The Making of Europe: Conquest, Colonization and Cultural Change, 950-1350 by Robert Bartlett [1] is an excellent book on the subject.

[0] https://en.wikipedia.org/wiki/Technological_determinism

[1] https://www.amazon.com/Making-Europe-Conquest-Colonization-C...