Instrument histories are usually told as national stories. This one is a story about movement.

The route

The oud reaches Iberia with the Umayyad court, and the figure most associated with its transmission is Ziryab, a musician who left Baghdad for Córdoba in the ninth century and is credited with adding a fifth course. From Andalusia the instrument moved north, and by the Renaissance the European lute was a distinct instrument with frets, a different tuning and a written repertoire.

What the frets changed

Adding frets fixes the pitches available, which suits a music organised around harmony and modulation between fixed keys. Removing that constraint — or rather, never adopting it — keeps the intervals of the maqam system available, including the ones that a fretted instrument cannot play. The two instruments diverged because the music they served had different priorities, not because one of them advanced.

It is worth sitting with that when the word "lute" appears in an English music history. The etymology is right there in the article, and the shared ancestor is closer than the two traditions usually acknowledge.