Breaking up monopolies gives us more free markets, and is a move towards capitalism, not away from it.
It's fair to say it's a non-capitalist power, I think. It's the government interfering in the operation of companies instead of allowing it to be entirely controlled by the market players - for good reason, of course.
A capitalist alternative would probably look more like levying fees or capping prices to try and balance the market... which is something that also happens from time to time.
Even fees and price caps would not be considered capitalist or free-market - they both interfere with the market dynamics. In all cases, we need to interfere with the free market to improve goodness for society as a whole.
But we don't need to attach moral connotations to this – the companies have done nothing illegal, and the executives are doing their jobs. The issue is when technology is applied to natural free markets, a monopoly logically results, which kills the market if left unchecked.
Not sure exactly what it is, but it’s more a societal move that smells a bit of socialism. Google is a capitalist company in a capitalist system, but the breaking up companies / anti trust is a non-capitalist power above it that is willing to sacrifice money to create societal wealth.