My probability on this subject evolves with lived experience: the impact of local events on travel planning is just one factor among others, not always predominant.
The probability that a local event is the determining factor for travel planning is, in my opinion, about 20% for most people.
For many, financial constraints or fixed holiday dates have an 80% probability of dictating the choice even before considering an event.
For example, a family that can only travel in August due to school holidays will prioritize the availability and cost of flights and accommodations, even if an incredible festival takes place in June.