Consciousness is an issue. If you write a program to add 2+2, you probably do not believe some entity poofs into existence, perceives itself as independently adding 2+2, and then poofs out of existence. Yet somehow, the idea of an emergent consciousness is that if you instead get it to do 100 basic operations, or perhaps 2^100 then suddenly this becomes true? The reason one might believe this is not because it's logical or reasonable - or even supported in any way, but because people assume their own conclusion. In particular if one takes a physicalist view of the universe then consciousness must be a physical process and so it simply must emerge at some sufficient degree of complexity.
But if you don't simply assume physicalism then this logic falls flat. And the more we discover about the universe, the weirder things become. How insane would you sound not that long ago to suggest that time itself would move at different rates for different people at the same "time", just to maintain a perceived constancy of the speed of light? It's nonsense, but it's real. So I'm quite reluctant to assume my own conclusion on anything with regards to the nature of the universe. Even relatively 'simple' things like quantum entanglement are already posing very difficult issues for a physicalist view of the universe.
My issue is that from a scientific point of view, physicalism is all we have. Everything else is belief, or some form of faith.
Your example about relativity is good. It might have sounded insane at some point, but it turns out, it is physics, which nicely falls into the physicalism concept.
If there is a falsifiable scientific theory that there is something other than a physical mechanism behind consciousness and intelligence, I haven't seen it.
Boltzmann brains and A. J. Ayer's "There is a thought now".
Ages ago, it occurred to me that the only thing that seemed to exist without needing a creator, was maths. That 2+2 was always 4, and it still would be even if there were not 4 things to count.
Basically, I independently arrived at similar conclusion as Max Tegmark, only simpler and without his level of rigour: https://benwheatley.github.io/blog/2018/08/26-08.28.24.html
(From the quotation's date stamp, 2007, I had only finished university 6 months earlier, so don't expect anything good).
But as you'll see from my final paragraph, I no longer take this idea seriously, because anything that leads to most minds being free to believe untruths, is cognitively unstable by the same argument that applies to Boltzmann brains.
MUH leads to Aleph-1 infinite number of brains*. I'd need a reason for the probability distribution over minds to be zero almost everywhere in order for it to avoid the cognitively instability argument.
* if there is a bigger infinity, then more; but I have only basic knowledge of transfinites and am unclear if the "bigger" ones I've heard about are considered "real" or more along the lines of "if there was an infinite sequence of infinities, then…"