This question seems like a big opportunity for casual social science conjecturing which may or may not be productive. I hope I can clarify a couple of things in my response.
According to your supporting statement, your question is "what are the possible explanations for why so many mathematicians you look up on Wikipedia are Jewish?" For the purposes of this answer I'm going to assume we are talking about one monolithic group with genetics and culture in common so that I can speak hypothetically (while acknowledging that others have challenges to that aspect of the question, and that they are at least worth thinking about).
One explanation could be that the group is actually better at math. To just ask why this group is better at math, however, would be to assume they are better at math (so I won't do that). It is not actually demonstrated by the wiki search mentioned. If there is more support for this sort of explanation--for instance, a difference in the comparison of means as part of some quantitative study--we could search for an explanation of why those means are different, and look to culture, perhaps. But we are not actually at that point, unless someone provides such evidence.
Another explanation we could conjecture about is that there might be similar means in the Jewish population and other populations, but there might be a greater variance in the data. Meaning that good Jewish mathematicians become more accomplished and thus are among the most famous mathematicians. And, if the means are similar, there would be similarly exceptional low achievers in the same population (or more slightly less accomplished mathematics users-- depending on the shape of the curve). We would look for a different sort of explanation if this is the quantitative difference we noticed in comparison of Jewish and other groups.
There could be cultural reasons that some accomplished Jewish mathematicians are better supported for some reason. Or that they have happened to be in groups at opportune places or times (enough to make really important contributions, but not in great enough numbers to change the mean over a reasonable sample of Jewish people). Yes, smart people "math better" but they do it even betterer in groups.
Conjectures are great starting points for research questions. But outside of using them for that purpose (to propose research) or having actual research and discussing how to extend from that research, I think we enter a realm of imagination rather than scientific enlightenment. One benefit of good social science is that assumptions must be made explicit. In casual conjecturing you will see assumptions pop up like dandelions and participants trample over them toward a possible explanation that catches their eye. I think I would be a lousy research assistant if I didn't point out that outside of scientific research, we often see a compelling conclusion driving whatever justification can connect things. And this is (at the very least) unfair to the groups of people subjected to our conjectures. Discretion and caution are called for. Even if we think we're saying something positive.