I reffed that battle, and it was his Machamp that used Protect+Wide Guard. Therefore all attacks that were targeting Machamp were protected against. If Leethoof had targeted someone else, it would have gone through.
Actually, I got the idea from Engi's match against Leethoof where his Carracosta used Protect + Wide Guard to cover his entire team. But since you bring up the fact that Protect has 0 priority when using it to cover allies, that makes sense. I'll get my commands up later today. :]