If a French company wants to expand into the Spanish market, they can localize their app all they want; if their prospective customers in Spain are already using a different app that works just as well, they're going to have a hard time convincing them to switch.
The same dynamic also applies within countries, where two interchangeable apps might dominate in different areas or demographics of the same country, without either able to gain significant market share from the other, but it's a bit rarer because of network effects, where people start using an app because they know someone else using it and the app with the most users grows the fastest, eclipsing the competition.
Cross-border network effects in Europe are much weaker than within countries, and not much stronger than between European and non-European countries, so if a company manages to dominate their niche across all of Europe, they'll probably also win in much of the rest of the world.
