Probably the most famous miscalculation of competitive threats was the total lack of concern by Kmart for the then smaller Walmart. Kmart had their sights on the industry leading Sears and forgot that as they were looking to feed on a fish that another fish might be looking to eat them.
Some will note this is the exact opposite of the cartoon as the fish shown are going after smaller fish. That is because the business world works in both directions. Just as big corporations are looking to gobble up smaller companies that can complement their offerings littler companies are striving to overtake their next largest competitor.