Why Castile seems closer to SW France than Catalunya is?

[Tenma de Pegasus]

Castile La Mancha appears marginally closer

https://image.ibb.co/gKWmqf/EURO-PCA-v3.jpg

[Saint-Glinglin]

Probably because of the basque influence.

In SW France the toponymy shows the presence of a basque (or basque like) language before the romanization of the area. This fact is confirmed by Caesar, I can't quote the excat passage, but in his Gallic War he states that the Aquitani (people from SW France) aren't Gauls, nor Germans.

The influence in Castilla - La Mancha is more tricky. It's probably due to the reconquista and repoblación patterns, where people from N Spain (Basque country, Cantabria, Castilla Vieja) went to establish in this area. Some parts of N Spain have some basque substratum in the same way as SW France does.

In Catalunya proper, you don't have much basque influence. That would explain the difference.

If this topic interests you, you may want to have a look there : https://en.wikipedia.org/wiki/Basque_language

Especially at the history paragraphs.