Well the corporate pressure we are oh so familiar with today did not evolve until 1999. Before then it was a corporate mentality of, "as long as it sells, make it."You got 2 out of 3, it wasn't because of corporate pressure, since that always existed even if the teams were much smaller. Of course it did help that a team of 10/20 people could pump out a game in a year or two max, but the biggest reason was that we had enormous jumps in technology in a very short timeframe.
There were constant innovations in IC as well as multiple fabrication node jumps that meant huge and cheap performance jumps very easily, relatively speaking. The tech has matured quite a lot though, the number of transistors in GPUs/CPUs/APUs number in the billions now, and on every platform, the energy requirements are becoming a challenge, while it's becoming incredibly challenging to go smaller in fabrication nodes.
Acitivision See 1997-2008
Electronic Arts see 1991-2007