Why has the UN Charter remained a central plank of international order, even though it was formulated in wartime by only a few of the victorious powers?

Extract

[...] It is also a multilateral treaty which in respect of the agreements, rights and duties it confers on its signatories and members is an important source of international law. Its genesis began in the very moment in which the collapse of the League of Nations and consequently of its Covenant became evident. The Charter was signed in San Francisco on 26 June 1945 and was ratified by fifty-one states and came into being on 24 October 1945 (known as United Nations Day). [...]

[...] It has succeeded in adapting itself in the face of political reality in an unanticipated progress which has gone far beyond what may have expected those present at the Dumbarton Oaks Conference and the San Francisco Conference and thus remains a central plank of international order. Furthermore, the United Nations is the one and only intergovernmental international organization (it is the second attempt at creating an intergovernmental organization) and it is the only international organization recognized in the whole world. [...]

[...] In our opinion, it can only make the will of having peace much stronger having known the atrocities a war can bring about. We can take the example of the European Union for a comparison. The EU finds its roots in 1951 (thus a post war project) and now shows a great success. The European Union can be considered an instrument of peace as well, as that is what it is doing right now and because one of its first objectives was to promote peace after a wounded and deconstructed Europe was left to its citizens by the Second World War. [...]

[...] With all these minor changes, the UN Charter can hope to still remain a central plank of international order. Moreover the fact that the changes are minor shows how complete and intemporal the Charter is. The reforms we have just cited are the official ones proposed by Kofi Annan but other people say there are other things to change. For example, there is a need to change some things in the Charter as some major powers have tended to deal with each other outside the framework of the UN (US intervention in Iraq not under UN flag). [...]

[...] Some people will answer to the fact that it was formulated by only a few of the victorious powers by saying that 50 nations then ratified it (not obliged too, if you sign it this then means you agree with its terms and objectives.) Plus, this Charter was not the result of the work of any single nation or a group of nations, large or small but of a spirit of give-and take, of tolerance for the views and interests of them. [...]