Maybe today it’s much less so, but it’s well known that Ashkenazim had some kind of advantage in terms of their “connections.” In many fields it was hard for Mizrahim to get accepted into elite ranks like the Supreme Court. You can see there was an effect—you can’t ignore that.
Are you telling me there is no discrimination between Mizrahim and Ashkenazim, basically? Isn’t that a bit like ignoring the rest of the picture, where you clearly see an Ashkenazi majority in certain places? Again, maybe today it’s less so, and that’s encouraging, but in the past it was much more obvious. So my question is: what caused it in the first place? Assuming we agree that we’re all equal in ability regardless of community, what nevertheless caused this discrimination?

You’re mixing together different areas and still not clarifying the question. First, the fact that there are differences does not mean there is discrimination. Discrimination is a deliberate and unjustified act.
As for the reasons, there are many, but I don’t think this site—or I—am the address for sociological research, certainly not in such a general and vague formulation.

I’m writing this to break the taboo around “racism” (in quotation marks).

I haven’t researched the matter, but it seems that Ashkenazim start out with some kind of advantage. Maybe genetics, like IQ. Or maybe it’s cultural, like an academic orientation and the like.
It’s absolutely not necessary that this is true, but it does seem quite plausible, and no one says it because it’s “racist.”
All the Jewish Nobel Prize winners (if I’m not mistaken) are Ashkenazi. A bit suspicious.
You’re allowed to notice facts, like how Blacks in the NBA have wildly disproportionate representation, or that they are involved in crime at massively disproportionate rates. Of course, that can stem from all sorts of reasons: cultural, genetic, or maybe the whites are to blame for everything (the common view).
As for the NBA, it’s very hard to believe that this is the result of culture (I’m not talking about a culture over many generations that affected genetics, which is definitely possible and presumably also true).
You’re also allowed to notice that certain genetic groups are more academic and maybe even, heaven forbid, “smarter.”

It’s very important to note that all these phenomena speak about the group and the average. Most individuals in all groups overlap, and the difference shows up at the extremes (having lots of Blacks in the NBA doesn’t mean a specific Black person is necessarily good at basketball. Likewise, an Ashkenazi can be stupid and a Sephardi can be a genius).

David, you’re repeating a common mistake. The number of Mizrahi Jewish Nobel Prize winners is probably no smaller than that of Ashkenazim. This was brought up here on the site in the past (for some reason I can’t find it now).
I’ve now found two sources on Google:
https://www.makorrishon.co.il/opinion/589039/

https://he-il.facebook.com/hakeshet/posts/%D7%90%D7%96-%D7%9B%D7%9E%D7%94-%D7%96%D7%95%D7%9B%D7%99-%D7%A4%D7%A8%D7%A1-%D7%A0%D7%95%D7%91%D7%9C-%D7%9E%D7%96%D7%A8%D7%97%D7%99%D7%9D-%D7%94%D7%99%D7%95/637202729631217/

By the way, in my opinion it also isn’t logically correct to say that most individuals are the same and the difference is only at the extremes. On the contrary, reason suggests that the extremes are דווקא closer to each other. There are geniuses and complete fools everywhere; the question is how much and what there is in the middle.

Mainly what I wanted to convey is that it should also be permissible to think that maybe there is no discrimination, and Ashkenazim are simply more suited to the specific roles. Maybe not. But it seems you’re not even allowed to think about it.

I’m glad to see that this is a mistake regarding the Nobel Prize.

As for differences at the extremes: it’s hard to define the middle. It’s a common mistake to call a random person in a group an average person—you may have met the most extreme one. What I meant was that if, say, there are 100 Ashkenazim and 100 Sephardim, and, for example, the Sephardim are 10% more charitable, then we would see 10 Ashkenazim at the bottom of the scale—remarkably hard-hearted. 90 Ashkenazim and Sephardim in the middle, and 10 Sephardi saints of the generation at the top.

You can see this in many fields.
From my impression, Jews are terribly bad at athletics, and still stand out very strongly in almost every intellectual field.
From my basic acquaintance, Blacks aren’t nearly that good at basketball to justify the crazy overrepresentation in almost any league you’ll find.
Etc. etc.

By the way, the Facebook post you attached actually helps the direction I’m thinking of: “academic culture,” which European Jews mainly brought to the table.
It claims that more Sephardim won the Nobel Prize than Ashkenazim relative to their percentage in the population—eleven winners in all. How many of them are European Sephardim like Niels Bohr? That might perhaps point to European education and academic culture as the motif, and not necessarily genes… I’m totally in favor.
So it would still be worth considering the possibility that maybe Ashkenazim, or European Sephardim, get more certain positions because they really are more suited to them.