PC games have had network play for a long time. Doom on DOS had LAN play over IPX way back when. Quake brought us the concept of playing over TCP/IP and the greater internet.
What were consoles doing at this time for network play? Almost nothing. The Dreamcast brought dial-up three years AFTER Quake was being played on 10mbit/s LANs.
For that reason, PCs dominated online gaming, and drew the people in. With the people came the market share, and with the market share came the flood of developers.
Fast forward a decade, and all consoles now have online play. Home internet connections are fast and easy to set up, and all the consoles have standard connectivity via wired or wireless connections. So the masses switch back to consoles that are cheaper to purchase, don't require as frequent upgrades, and are nearly maintenance free (the occasional update, but certainly not the same effort as maintaining a Windows PC).
From a commercial perspective, console gaming gives you access to a wider audience and a standard platform (no guessing which video card or CPU your customer is using).
The glaring upside of the home PC of course is the $0 development tools and $0 distribution. For indie devs, this is a huge way to get your product and talent noticed, and invariably end up writing console code for profit.
