Things can be obvious if they are simple. If something complicated is obvious, such as anything that anybody seriously studies, then for it to be simple you must be abstracting it a lot. When people find such things obvious, what they often mean is that the abstraction is so clear and simple its implications are unarguable. This is answering the wrong question. Most of the reasons such conclusions might be false are hidden in what you abstracted away. The question is whether you have the right abstraction for reality, not whether the abstraction has the implications it seems to.
e.g.1 I have heard that this is obvious: reality is made of optimizers, so when the optimizers optimize themselves there will be a recursive optimization explosion so something will become extremely optimized and take over the world. But to doubt this is not to doubt positive feedback works. The question is whether this captures the main dynamic taking place in the world.
e.g.2 I have thought before that it is obvious that a minimum wage would increase unemployment usually. This is probably because it’s so clear in an economic model, not because I had checked that that model fits reality well. I think it does, but it’s not obvious. It requires carefully looking at the world and at other possible abstractions.