In other words, one should think of network effects as comparable to a natural monopoly. In a network effect product as for a natural monopoly, once you have market dominance, that dominance persists not because of any anti-competitive behaviour by the company that owns it (even if there appears to be plenty) but because of the mechanics and economics of the product. 

changing who owns Instagram doesn’t alter the network effects that make Instagram strong, nor YouTube, nor WhatsApp, because, as for Office or Windows, the network effects are internal to the product. You don’t use WhatsApp because Facebook owns it. Google Search isn’t far ahead of Bing because it also owns Youtube. And yes, just as Microsoft was accused of doing all sorts of things to cross-leverage its businesses, so are these companies, but that’s ultimately peripheral - the market dominance comes from the products themselves.