>>512934873
They would have traits directly taken from sanskrit, instead they only have similarities

Look at the numbers alone, none of them look like they descend from Sanskrit

Avestan one=Aeva
Sanskrit one = eka

Compare that to Old English and German where Old English comes directly from German

German one= ein
Old English one = an

And that's just a single number, linguists study the entire language, there's no way they would miss if the Iranians languages descended from Sanskrit.

Instead Iranian languages and Sanskrit have a common origin but don't descend from each other, hence the concept of a proto-Indo-Iranian language. There is no other logical conclusion.