Why you can’t have a useful conversation with a lot of people
Imagine a set of concentric circles where the proximity to the centre represents the depth of conversation and the centre represents the depth of conversation necessary to resolve any particular problem or question.
Simple situations can be represented by a small number of circles; complicated situations require a much larger number of circles. That is, more complicated situations require more depth of conversation to resolve.
When there are a lot of people, conversation tends to be shallow, simply because of the time it takes to listen and respond to everyone. The conversation ends before it ever gets deep enough to resolve the situation.
When there are less people, it’s much easier to get to depth and reach resolution.
Granted, the smaller group also needs to have sufficient relevant context and knowledge to be able to get to necessary depth, but as a general rule, if you want to have a useful conversation, keep the group small.