The reason why the USA has so many tech gigants and the EU doesn’t has nothing to do with talent or market size, but instead everything with low taxes, lax regulations, massive tax breaks and generally the political will to shovel billions into private companies and letting the population pay the bill for it.
Ireland and Malta are the countries most overseas tech companies (and gambling and porn companies) choose as their European seat, not because they have an amazing amount of great skilled talent, but because they have really low taxes and regulations.
Also, the EU really doesn’t want companies that are so big and important that they are more powerful than the government.
Lastly, another issue is that the EU, when handing out money to companies, prefers the Airbus model. Instead of concentrating everything into one city, like in Shenzhen or Silicon Valley, they like to spread everything out over all of Europe.