They have done it before on a budget limited squad under Simeone, why not now after spending?
Hopefully, Simeone will be able to handle the high expectations around the team, otherwise, the players might feel like they can win a game before even playing it, and that usually not goes the way you want it to go (as a Real Madrid fan, i know this lol).
Atletico Madrid or Diego Simeone will never get cocky ahead, from my perspective the team treats every match with the same preparation, except there's something bigger to play for.