The single-game system of the Champions League final is supported by his high level. In European football and even the world football, the Champions League is the highest-level event, and it is a supreme honor for any stadium to hold the Champions League final.
The teams that entered the Champions League finals were the strongest teams in the world at that time, and the people who paid attention to them were no longer mainly composed of two teams of fans. Therefore, any stadium with convenient transportation in Europe can attract enough enthusiastic spectators. It is the economic benefit brought by the single-venue system, which refers to the bidding for the final venue. This is a win-win activity. And all this needs high-level support.