Flight search engines filter prices. They do not quantify the influence of an event.
A festival or a match increases prices, yes. But it is not the only cause.
Seasons, overall demand, everything plays.
A comparison tool helps to buy, not to understand the market.
For example, Google Flights shows an expensive flight to Sapporo during the Yuki Matsuri, but it does not explain why the flight is expensive, only the price.