HaSh-m always punishes "Midah ke'Neged Midah" (i.e. the punishment fits the crime). How did this apply here?
Rashi: "'The dread of the evildoer shall befall him' (Mishlei 10:24).... What they had said, 'lest we be scattered' (11:4) is what happened to them." 1 They had united in order to rebel against HaSh-m, so HaSh-m caused infighting among them by changing their language, thereby causing them to break up.
Rashi (to 11:7): HaSh-m responded to their plans with the same word they had used, "Havah." Refer to 11:7:1.1.
Maharal: Refer to 11:4:1.3:1.
Gur Aryeh: What is Rashi explaining? The text of HaSh-m's verdict was, "let Us descend and mix up their languages" (11:7). We might think that the Dispersion merely followed as an automatic result. Here, the verse adds that HaSh-m scattered them (as an integral part of the decree), because that is precisely what they had said they wanted to avoid.
