Crimea didn't have control over Ragnell.
Begnion did. It was their original leader who used the sword, it was their sacred treasure. Which makes it even more likely that it went to either Ike or nobody: that wasn't even the country Ike called home. Makes it even less likely that one of his decedents (related to the ones that took over his Mercenary group in Crimea and most likely stayed there) would get the sword later on.
They also would have wanted Ike to be safe in his travels with the hopes of him coming back. Remember, the blessing was tied to Ragnell specifically, not Ike himself. Wouldn't you want the person who saved the word to be safe while travelling?
Logically speaking, it pretty much has to be Ike directly. He killed the Goddess, he gets to keep the nice shiny sword, he took it with him when he left because screw the rules. To me, Praim being a faker/idiot and having a fake Ragnell is more likely than him being from Boyd/Mist.