Post History

Why was Spanish the only Romance language to loose the initial "F" in Latin words?

Going through the History of the Spanish language article in Wikipedia, I read the section [Latin f- to Spanish h- to null](https://en.wikipedia.org/wiki/History_of_the_Spanish_language#Latin_f-_to_Spanish_h-_to_null) some interesting insight:

> F was almost always initial in Latin words, and in Spanish most of them passed through a stage in which the consonant eventually developed to [h] and then was lost phonologically.

And also:

> The change from /f/ to /h/ occurred in the Romance speech of [Old Castile](https://en.wikipedia.org/wiki/Old_Castile) and [Gascon](https://en.wikipedia.org/wiki/Gascon_dialect), but nowhere else nearby. Since both areas were historically bilingual with [Basque](https://en.wikipedia.org/wiki/Basque_language), and Basque once had [h] but no [f], it is often suggested that the change was caused by Basque influence. However, this is contested by many linguists.

So it is interesting to see that this is indeed the case just for Spanish. See some examples:

| Latin  	| English 	| Spanish 	| Catalan 	| Portuguese 	| Italian 	|
|--------	|---------	|---------	|---------	|------------	|---------	|
| filum  	| thread  	| hilo    	| fil     	| fio        	| filo    	|
| filius 	| son     	| hijo    	| fill    	| filho      	| figlio  	|
| furnus 	| oven    	| horno   	| forn    	| forno      	| forno   	|

As indicated in the quote, this is just specific to Spanish. But, what other theories are there to explain this? I couldn't find them. Does the usage of Arabic throughout the Iberian Peninsula during the VIII to XVI centuries have any influence on this different evolution in contrast with the other Romance languages?