I feel the main issue was that the US historically was the place to go if you want to study or work with the "best" tech minds so talent flocked there. During the industrial revolution you couldn't so easily just pack up and move across the world.

Even now where I don't think that holds true so much (there are small pools of talent elsewhere, e.g. Stockholm is hot right now), a good senior engineer in Europe may be able to get €100k, and you are looking at 2 or 3 times in the US, so it's still attractive to relocate.

Cultural differences (mainly language barriers) made it hard for somewhere like that to evolve in Europe. Yes everyone in tech speaks English, but if you move to say Poland and want to rent an apartment or see a doctor, you would have had a hard time without at least a basic understanding of Polish. It's completely different from someone moving from Texas to SFO.

Ironically all the immigration of Russian speakers over the last few years has actually helped embrace English in these countries, as for nationalistic reasons they don't want to embrace Russian.

In the 2000s and early 2010s London was the tech hub of Europe (English speaking, many high ranking universities in the vicinity), but Brexit f***d that up.