so essentially,
valve: lets make a good game that can survive on its own, but we wont give it comp support (tf2 comp is born, the SSBM of first person shooters, it wasnt designed for comp, a fast arcade shooter with some depth and balance. ) hopefully we can experiment with this game for future titles, csgo for example with our source code.
blizzard: ha, so they want this style of game with comp support, lets see if we can rip apart valve's underground scene by making our version with major comp support and milk it, hell lets make a 2nd game later on, why not manipulate a desperate player base not aware of how good they got it? yea they are fersure not a major esports, but they are small and support each other, they have lots of awesome things. they really don't appreciate what they got. lets take them for a ride.
edit: also, *blizzard rubbing hands menacingly* this should be a good revenge plan, I mean shit, how could we had known dota would had been a big deal? I mean shit, we just thought people really liked playing world of warcraft for years with no major changes or alternative game modes.