Ordoliberalism is the German answer to the question of what a liberal should have learned from the interwar catastrophe, and it differs from every other liberal school on the point that matters: it does not believe the market is natural.
The Freiburg school formed under the Nazi regime, which is essential to understanding it. Eucken and his colleagues watched cartelized heavy industry make itself indispensable to a totalitarian state, and concluded that private economic power is as dangerous as public power and tends to convert into it. Laissez-faire was therefore not innocent: leaving markets alone produces concentration, and concentration produces the political conditions for tyranny.
Their conclusion is that competition is a public good requiring construction and defense. The state's task is to establish the framework — the Ordnung — within which competition operates: stable money, open markets, private property, freedom of contract, liability for one's own losses, and above all vigorous antitrust. Within that frame the state should not intervene in prices, wages or outcomes. This is a strong state and a limited one at the same time, and the ordoliberals were explicit that a weak state captured by interest groups was the real enemy.
Röpke and Rüstow added a cultural dimension the Freiburg economists left out, arguing that a market order needs to sit inside a society of small enterprise, property-owning families and religious observance if it is not to corrode itself.
Erhard put it into practice as economics minister in 1948, freeing prices against Allied advice, and the Wirtschaftswunder followed. The doctrine became the German consensus, and through Germany it shaped the European Central Bank's mandate, the stability pact, and the terms of the eurozone crisis — where its insistence on rules over discretion was read elsewhere as moralism.