After the chaos report came out in the mid nineties and made the public statement that 53% of evaluated projects where "challenged" and only 16% of them could be considered "successful" a lot of people started to focus on the errors that supposedly had been made in the 53% of challenged projects. And from the tries to eradicate those errors from all future projects a lot of the so called ”heavy“ processes where born. For the curious: the remaining 31% of projects got cancelled before they ever saw the light of day.
Yet some people focused on the question what the 16% of successful projects did differently – in line with the old coaching mantra of "catch them doing something right." Amongst other things a lot of these projects followed what today would be called an agile approach - kind of living and breathing some of the principles behind the agile manifesto even though that didn't even exist at that time.
Although the principles could be weighed differently one of the key concepts in my perception always was
The most efficient and effective method of conveying information to and within a development team is face-to-face conversation.
which also requires the teams to be of manageable sizes – the magic number 7 ( plus or minus two ) comes to mind.
Because the number of required communication lines grows exponentially with the number of team members it quickly gets impractical to have face-to-face conversations with larger teams and this in turn contradicts the whole idea of "scaling agile."
Of course it's possible to develop software in an agile manner with more that just one team, but then something else has to come into play. At least "Agile" as defined by the agile manifesto doesn't account for scaled agile. Scrum tried to address this topic with the Scrum-of-Scrums, but I think nowadays there are more obvious ways. Like integrating agile teams via a lean organization. You might want to give it a try.