edit: The first company that is successful in a space will accumulate the money and the clout to keep competitors out of the industry and influence regulation to protect their position. The only worry such a company has is that a larger, more incumbent company in a related industry will undercut them by taking a loss, either through expensive lobbying or aggressive underpricing.
Since Reagan, the US has openly been reducing taxes and extending subsidies and bailouts to the largest companies, and finance/media rules have been gradually dismantled enabling politicians to take better advantage of indirect payments.
The reason incumbents have been more successful since 1980 is a direct result of government corruption, and is no different than similar patterns within other corrupt economies.
edit2: I forgot the incumbent option of buying the competition though the furious M&A that has also increased steadily during the same period, along with increasing weakness of antitrust legislation which encourages the behavior.
It's sad that we live in a time (due to computing and the internet) when starting or expanding a new or small business is less capital intensive than it has been in history, yet the incumbents have used regulation to make themselves more entrenched than they've been in nearly 100 years.