Coaches and their national soccer teams: Is there a trend to success?

With the Socceroos bowing out albeit in a unfortunate way, the quarterfinals now has no team that is coached by a Dutch. They have as they say shot their load.
The eight that have made it to the quarterfinals and their coaches
Brazil- Alberto Carlos Parreira
Portugal- Luis Felipe Scolari
England- Sven Goran Erickson
France -Raymond Domenech
Germany- Jurgen Klinsmann
Ukraiine- Oleg Blokhin
Italy- Marcelo Lippi
Argentina- Luis Pekerman
Six out of the eight coaches are indigenous. The two exceptions being Luis Felipe Scolari and Sven Goran Erickson. They coach Portugal and England, respectively. Out of these eight countries, 6 have won the World Cup. Out of the successful six, all have been coached by indigenous coaches. There are no exceptions.
Brazil- 5 world cup titles, all Brazilian coaches, Vicente Feola (1958), Aymore Moreira (1962), Joao Saldanha (1970), Carlos Alberto Parreira (1994), Luis Felipe Scolari (2002)
England- Sir Alfred Ramsey (1966)
France- Aime Jacquet (1998)
Argentina- Cesar Luis Menotti (1978), Carlos Bilardo (1986)
Italy- Vittorio Pozzo (1934, 1938), Enzo Bearzot (1982)
Germany- Sepp Hereberger (1954), Helmut Schon (1974), Franz Beckenbauer (1990).
The trend says that to be successful at the highest level, the coach should have the same nationality. The only World Cup winning country that has gone overseas to look for its coach is England. The other World Cup winning teams have decided that home cooking is the best.
There also seems to be a suggestion that if you want to build the teams from a grassroots level and help achieve success by qualifying for the World Cup, then non-indigenous coaches are better than the ones at home. Out of the eight new teams in the World Cup, six were coached by non-indigent coaches. The Soca Warriors, the Socceroos, the Black Stars, the Cote D’Ivoirians, the Angolans, and the Togolese. Only the Ukraine and Serbia-Montenegro squads relied on coaches of their own nationality.
The impetus given by coaches that are non-indigent is invaluable because it appears that they are not part of the social and political fabric of that nation. Hence, they do not belong to camps, or have ethnic affiliations that can come in the way of conflict resolution. Greater objectivity leads to a more successful team being rebuilt. However, it would appear that to be successful and go all the way to the top, i.e., win the World Cup, you need someone who is as conversant with the language and the cultural mores of that country, which seems to inevitably be one of your own.