My experience is with Earth Science and often they put out adverts for students to study specific topics. They actually have to apply for funding with the topics before even looking for a student.

If you had a topic in mind you would have to convince a professor or supervisor to then pitch that in a funding round. Often they have their own topics they want studied so it would have to be a convincing topic.

I actually don't know how History or Arts etc are taught or where you are but here, it's the supervisors that pick the topic for the student (99% of the time anyway). It would often be in the field that the professor is studying usually supporting their work. Maybe in a highly resourced university there may be some blue sky research but as far as I'm aware here, they're all funded to support the work of the professor with topics chosen or suggested by them.

I realise it may vary from country to country and field to field though.

I've got quite a lot of exposure to academia although I'm not in it and there an element of truth to what he's saying, even though it's not like a deliberate conspiracy.

For instance you talk about PhDs wanting to disprove things, or scientists as a whole.

Any research would have to be signed off by a HOD. The HOD definitely didn't get there by their research into alternative views, more than likely has extensive papers in the current model. So they have a reason to decline research into these alternatives as they think it's a waste of time as theyre invested in the standing theory. The professor probably didn't get to where they are in papers in alternative views as their H score will be a lot higher from being cited with views inline with the consensus. Plus a professor wouldn't want their name attached to a paper that might be considered 'alternative' because 9 times out of 10 it would be shown to be wrong and there's a reputational cost to that.

Then of course all the other ways to get funding to do research goes to committees and boards which again, often are staffed by people who have heavy investment in the accepted views.

These things combined with limited resources in research funding does lead to a very narrow research field.

It would be extremely difficult to actually get funding or the support to study things that goes against what is accepted.