That these uniforms were destined for Syria and not the banlieues of Paris, Marseille, Brussels, etc is but a small saving grace. That time will soon come.
If ISIS is a US-created and -supplied organization, it would make sense that these uniforms would be made in the US or elsewhere to US standards and shipped to Saudi Arabia Arabia. International shipping is a tangled web, but it would make as much sense that Spain was the final destination as Syria. These uniforms may well have been intended for ISIS members already in Europe.
Look at it this way. The fertilizer stockpile surely was not going to Syria. Why would the uniforms be going to Syria?