LVMH is very very far from being a monopoly. Luxottica is under investigation currently just like the tech giants are (and received already fines just like 2 years ago). De Beers was the target of antitrust multiple times, had to cancel a few deals and change some commercial practises because of it. Could have gone further IMO but at the same time the consequences on consumers are limited given how niche a market vs the tech sector.

There's small luxury producers all over Europe, they just aren't as successful internationally as LVMH.

And even then it's easier to launch a new luxury bag than a mobile OS...