Chelsea and Inter sat perversely deep, so the likes of Cambiasso, Zanetti, Essien, Ballack, etc. could move up and challenge Messi knowing full well there was still a wall of defenders behind them so even if he beat them (and he often beat one or two men). teams in Lliga don't sit that deep (well, most don't) so there is often more space for Messi as defenders can't challenge him as freely, because if he beats them he could break into the more dangerous space behind them.
you also need a compliant referee, so you can kick the bejeesus out of him without getting punished. Inter and Chelsea thrived off lenient refs (the Portuguese guy in Sansa was even Mourinho's old friend and business partner) and just brutalised Messi. except Zanetti, he defended him straight-up, man-to-man. it no doubt helped that he's known Messi for years and years, but by gum he was fantastic.
god he's a legend.