> but what underlies the inability for firms such as IBM to continue to grow?
I think you've answered your own question with the examples you gave.
Alive companies: Environment hasn't changed much.
Dead/hobbled companies: Significant change in the environment around creating the product/service or distributing the product/service (or a substitute) which upended the competitive dynamic. 100s of companies try to take advantage of the new dynamic and the existing companies might win, but are just another 1 in the 100's who are vying to win the new game.