Thiago Silva was part of the best starting 11 of the Brasileirao at the time but well known outside Brazil he definitely wasn't. He was a pretty unknown quantity outside Brazil and there was hardly any more interest in him from European teams than now for Rhodolfo or Dede - in fact, at the time the hottest name among Cb in Brazil was SP's Miranda.
Actually, even Milan wasn't too hot on his heels and Inter had almost signed the guy - he was already given for an Inter player in Brzail - when Leonardo drew the board's interest on the guy and urged Milan to signed him and helped stealing TS from under Inter's nose, literary

... at the time, European/Italian media treated him as yet another experimental signing by Milan in an attempt to not spend big for a proper Maldini replacement. (see Rhodolfo

)
Other than that, TS arrived at Milan in the winter but couldn't be registered till next summer due to the non-EU limit so he spend the second half of that season training with Milan. That same summer Maldini retired, and considering the rest of our CBs (apart from Nesta) were Kaladze, Bonera, etc, TS literary walked into the starting 11 ... and the rest is history