I'm just trying to understand the idea of large scale 'Agile'
"Apply the principles that we found out to work so well in small groups - which is what makes small groups so successful, because only in small groups these principles can work - to large projects?"
Whom are you trying to be kidding?
Let me put it another way:
1995 to 2008: 7 plus/minus 2 is the ideal team size because of [the usual arguments]
2008 ff. : 'Agile' works so well, lets just apply it to the enterprise level
Yes I know: the 7±2 team size thing is way older than 1995 - I was referring to usage in the 'Agile' (capital A) community