It’s not so much when the Olympics are as that people are purposely moving travel outside that timeframe. Also, the Olympics actually are starting in July this year, so it’s right at the end of the peak season. Another factor is that the games aren’t just in Paris, many of the venues are spread out across France, so it is affecting a lot across the country.
For a lot of tourists heading there, the effect is that a good bit of hotel space, etc is eaten up, so they are deciding to go elsewhere. More, “hey, let’s avoid all that going on in France and go to Italy instead”, which in turn drives up the demand in Italy. Or, hey, let’s go in June instead of July…
That’s what I meant by the “ripple” effect that the games are having on European travel.