About your "existence of the Jews" argument, consider this scenario. Let's say I'm a scam artist. I get 10000 email addresses. I pick a stock. I send 5000 people my prediction that the stock will go up, 5000 my prediction the stock will go down, and invite all of them to buy my stock predicting service. The stock either goes up or down, and I send a second e-mail to the 5000 who got the right advice, along with the name of a second stock. I tell 2500 it will go up, and 2500 it will go down. The 2500 who got the right advice both times are intrigued, so I repeat the procedure, 1250/1250, and finally once more, 625/625. I now have 625 people who think I'm an amazing stock predictor,having picked right 4 times in a row. If I send them all one last email, guaranteeing my results, against splitting them into two groups, and inviting them to send me $1000 for my amazing, guaranteed, stock prediction newsletter, I think a significant number of them will do so.
Similarly, various groups and tribes die out eventually, but 1 will last longer than the others, just by random luck, and it does not show that the God of that group exists or is powerful. It's retro-diction, which is bogus.
And another thing, shouldn't g-d have delivered on more promises than mere existence? Shouldn't we be in a lot better shape, power and success-wise?