Everyone wins except the common man, who now must deal with the chilling effects of media and communication monopolies having the power of judge, jury, and executioner when it comes to speech. No need to censor people you don't like if you just capriciously censor people without warning or due process... people will censor themselves for you after that.
Remember the problem isn't that these people had platforms, the problem is those platforms accepted money to promote and advertise these people. I'm sure facebook loved having these people churning around their recommendation engines, they probably drove engagement like crazy. But now the backlash isn't worth the profit, so we all have to pay the consequences.
Remember that sunlight is the best disinfectant, and "deplatforming" these people might make them as personalities go away, but their ideas and propaganda will surely fester and grow in the darker corners of the internet. Milo is a joke even among the alt-right now, but his vitriol and invective continue to grow in popularity.