Simplified, many great old successes (old money, i.e the billionaires) and many new promising, but few in-between.
Is Borland actually a European company? It looks like it was started in California and has a headquarters in Texas. It is now owned by a company in the UK, but it doesnt really seem European to me.
> Borland Ltd. was founded in August 1981 by three Danish citizens, Niels Jensen, Ole Henriksen, and Mogens Glad, to develop [...] However, response to the company's products at the CP/M-82 show in San Francisco showed that a U.S. company would be needed to reach the American market. They met Philippe Kahn, who had just moved to Silicon Valley...
So yes, Borland is a US company, but founded by 3 Danish folks. That might indicate that Europe doesn't lack innovation or talent, but a large unified market with high purchasing power.
I'd say it would have been hard to sell anything that specific even elsewhere in the US at the time.
For example free education improves a software company's hiring prospects as there are lots of employee candidates available with good education. In some countries social mobility is a real thing. As a practical counter example, Sweden has massive taxation and something like most billionaires per capita and a very vibrant software and startup scene.
One could actually do some kind of survey what happens to European software companies. Take for example this one started by three Danish guys: https://en.wikipedia.org/wiki/Borland