Earlier quoted context omitted.
Aren't monopolies is what we end up by default if have no regulation at all? And yes, not every regulation destroys monopoly, but regulation is the only thing that could break one.
Are there any examples of monopolies being (successfully) broken up in Europe? Or do you posit that regulation stop them from forming?
A lot of these were international. Just read up on "Cartel capitalism".
https://www.cambridge.org/core/journals/enterprise-and-socie...
The European Steel and Coal Community (precursor of the EU) was also involved in the effort to stop these. In general this has been something the EU has been involved in since its inception and the best action against monopolies is to not let them form in the first place (why there is so few of them in general in most developed countries. Though that is now slowly changing it seems)