Earlier quoted context omitted.
These were because technology changed, not because of better competitors doing the same thinig
They did the same thing as far as the customer was concerned, only better, thereby offering a better deal to customers, who switched.
but it negates your point that lazy incumbents will get disrupted by nimbler competitors.
That mostly happens when the 'nimbler competitors' are in fact armed with a completely new technology, business model, etc.
ie, innovation is the key to change, not just decay of the old making way for more of the same, but more vigorous.