Yeah, Since Simeone taken over, Atletico Madrid was not rich at the time, around 20-30 on the richest club list. They grew up, increasing their revenue and exposure of UCL, they have Greizmann on 400K+, that how rich Atletico Madrid has gotten since 2011. Valencia and Villiard have been more successful than Atletico Madrid in 2000s, no one can top Barca/Real in the league and be more successful than them but Atletico Madrid is very doing well when you consider gaps between them and Barca/Real in revenue and powers.
We have our Atletico Madrid in England which is Spurs. If Atletico Madrid and Spurs show they can match the powerful club despite behind in success, the prestige of club, revenue, and trophies, I think Leicester City can do, they'll take it at slow to get better each time. Rome wasn't built in a day