I'd have to look again to be sure, but as I remember it Judah had no legitimate sons to carry forth his birthright as he mixed with a Canaanite which was against the rules. He wanted them legitimized, but the first two sons died as he tried to get that done, and the third had something to do with the term Jew - being both Israelite and Canaanite but illegitimate to both.

Another viewpoint of mine is that the true nation of Israel was scattered, and Levi's artifacts were stolen along with their practices - the ways and means, rituals, and beliefs, hijacked by the Babylonian invaders and corrupted.