Does not work like that.
Argentina and Messi were hugely criticised for 15 years and won fuckall with that "motivation" until the Copa win. If anything the team was infamous for crumbling in high pressure moments.
You need a good balanced group, team sprit, star players and manager to be a good national team. Motivation isn't enough on its own. With this Scaloni team, they have finally struck the right balance. They're levels above current Brazil and would win today either way.
of course, not saying that's the reason they won. But it is an extra motivation. Arch-rivals talking shit before match, you bet they are going to want to prove a point. Does it mean you'll win? not necessarily, it's football after all, you can be massively superior to the other team and still loose.
yeah, don't disagree with the last sentence. There's plenty of examples of it not working if your team is not well balanced. Arg 2010 comes to mind (granted Maradona as a coach is like that team did not have a coach at all

), stacked in attack, but everything else meh. Recent Brazil, etc...