I think much of that is because European customers (both private and business) tended to prefer American suppliers over suppliers from European countries that were not their own. That may have something to do with most people in IT being quite fluent in English, while European products were all-to-often half-heartedly translated from German/French/Spanish/Polish/Italian/Ukranian.

In many cases, well-established and well-liked European services have been supplanted by American counterparts that came later and were not really better in any way. They did usually have much more money to burn though, undercutting pricing until competition was dead.

I'm speaking in the past tense, because now for the first time in the couple of decades I can remember, there seems to be a somewhat commonly held preference for European suppliers.