Google, Facebook, Amazon, etc. do not "own" anything. They are businesses that exist in a fiercely competitive environment in which consumers have zero loyalty and will gladly switch to the next hot thing at the drop of a hat. These businesses are successful because they continually innovate and deliver products that people want. There's no guarantee that any of these companies will still be around in a decade, much less "own" the market they operate in.
And monopoly regulation put an end to that and allowed Netscape to come in and make it a competition.
It was really an absurd case considering that 100% of internet users use a free browser these days.
Netscape was selling their browser before Microsoft got smacked down by the DOJ.
In fact, Microsoft's bundling of IE with Windows was some of the strongest evidence showing that they were abusing their market position. By bundling a free alternative they basically destroyed the market of for-pay web browsers, and killed off Netscape while they were at it.