Because there are anti-Semitic conspiracy theories that Jews control the world, and they do so in large part by using oodles and oodles of money to control people. That may not be what she means, but it's why it's so important to be particular with one's word choice and not beat around the bush, so that these misunderstandings don't happen in the first place. That is to say, how you say something can be just as important as what you're saying. And when there's absolutely no reason to be vague and you have the characters to avoid these misunderstandings and be more clear, then, well, what exactly is the benefit of being vague in the first place?
I wouldn't accept that kind of sloppy wording from a Republican, I'm not suddenly going to lower my standards because she's a Democrat and in her case likely does mean well. There's just absolutely zero reason to be vague here, and tweet out stuff that either could be read as anti-Semitic conspiracy theory garbage or as valid criticism of real issues, when she could just be more clear in the first place and avoid that. There's just no reason or excuse to be tweeting stuff like that out, regardless of intent, as it does no one any good, doesn't help anything, and be so easily avoided and it's just all so unnecessary. And that's because regardless of intent, regardless of whether she means for it to be read those way, those kind of anti-Semitic conspiracy theories do real damage to the lives of Jewish individuals each and every day.
Like, she might not intend to do damage, and I'm ready to believe that. But that doesn't change that damage is done all the same all the time by comments just like that, regardless of whether it's intended that way or not, and that's why it's so important to do better and have higher standards and not be so careless with one's words. Like, I wouldn't accept it if a Republican had said this, because of the damage those kinds of words and statements mean regardless of intent, and I'm not going to lower my standards just because she's a Democrat instead. If anything, I expect more from her as I expect Democrats to be better than that and not make those kind of mistakes to begin with.
If people still don't get it, another way to put it is, hmm, maybe to compare it to Elizabeth Warren, and the conspiracy around her Native American heritage, or lack there of? It seems very likely that Warren didn't actually intend any offense to Native Americans and was just ignorant and sloppy in how the handled that mess. Nonetheless, regardless of whether she meant it or not, how she handled that stuff is the kind of thing that does damage to many Native American tribes even today and was just a series of unforced errors and very, very poorly handled, and as a Democrat myself, I expected better from her on that.
Same deal here. If people can get how Warren messed up with the DNA test stuff and all that, it's a very similar issue with Omar and these particular tweets. That no actual offense needs to be intended, and the damage is the same regardless of whether it was intended or not, because how you say something is just as important as what you're saying. So yeah, if people can get the deal with how Warren messed up even if they don't think she actually meant anything wrong at any point, but still messed up regardless of intent, it's a very similar with Omar here, if that makes any sense and helps you to understand the issues at play here.