I think their ‘favorite’ tag was based on an unbeaten streak of thirty plus games and winning a lot of friendlies 3-0 just before the WC. It’s the least overwhelming squad they’ve had since the late eighties, and I suspect that those results stem from a well organized team of players that fight for each other, all accept carrying Messi, and are both cynical and patient. They have a good defensive backbone in Emiliano, Romero, Otamendi (and Lisandro), and will get a goal from somewhere (Messi). They have a coach who makes sound judgements on how to change up the team to get the machinery working.
To me they are nowhere near favorites, but looking at the favorites (Brazil, France, Spain) and outsiders (Portugal, England, Netherlands, Kroatia) there are no teams there Argentina can’t beat with a good defensive performance and a bit of luck.