Have a look in the 4 regions trophy cabinets for the past 20 years and you will find the answer. The regions don’t have enough decent players to win anything, unlike the Irish regions, who do. Last season Ireland U 20’s won the equivalent of the 6 Nations. Leinster supplied 9 or 10 of the team in each of the games. It’s no wonder Leinster and Ireland are doing well. Munster also won the URC play offs, winning away in South Africa against all the odds.Gatland is able to bring the best out of them collectively when they play international rugby.
It’s no guarantee Wales will beat Argentina next weekend, but they are favourites to reach the semi final.