You are talking as if this is the first time Argentina has made the semis of a WC. In 1999, 2007 and 2015 Ireland was supossed to beat Argentina too. Didn't happen.
That first game vs England was the worst match I ever witnessed from an Argie side in any sport ever. The Pumas got to that game thinking they were the favourites and the pressure got to them, specially after England got down to 14 men. Now that they got it out of their system, I don't see them playing such a embarrassing brand of rugby again. That's clearly not even close to their real level. Argentina and England are probably going to face in the 3rd position match, I don't expect another no show from the Pumas.