The Western Liberal Education System is based on debate. Before someone says they are a conservative, and therefore are against the Western Liberal Education, the word "liberal" is using a different definition there. The Greeks had the "liberal arts"(free people skills), and the "servile arts"(not free people skills). Free Greeks were supposed to participate in their governments. They had many different types of governments from democracies to monarchies, but all had some level of politics involved. Therefore debate was important to all.
To teach debate, you need students from different points of view. Diversity in education is not a new invention, but actually part of Western education from the beginning. You also have a system that keeps reinventing itself through debate.
You would think that education based on meritocracy would be better, but it has failed compared to our western system. The Arabs, Chinese, Indians, etc. had education based on meritocracy, where there were tests to pick the best students, and then later tests to pick the best teachers from those students. At first you get the best of the best, but over time you get the best at taking those tests. You get teachers who are highly invested into the old knowledge. Some of the oldest universities in the world still teach science from a thousand years ago, because that is what is on the test.
In the west, many, if not most, professors would have PHDs. They have extended the knowledge of humanity in some way, and have defended their thesis in debate.
Or so the system is supposed to work. I am not saying it is always perfect, but it is a darn good system, and has done us well.