The Psychology of Interpersonal Behaviour - Michael Argyle

I found a chapter in The Psychology of Interpersonal Behaviour by Michael Argyle that I think explains simply how such a community would come to exist.

"The basic theory of a group is simple, there are two motivations for joining one; to carry out a task, play a game etc., and to enjoy the social interaction and sustain relationships. All groups have activities, though the balance varies. People often join a group for economic or other non-social reasons in the first place; they then become involved in group activities, find these satisfying and become attached to the group. A group of friends may want to enjoy each other's company, but they have to do something, i.e. a task must be devised; leisure groups provide a solution to this problem.
Group formation A group, by one definition, is a number of people who are attracted towards the group, either to activities or to each other, usually both. Such 'cohesiveness' can be measured by the proportion of choices, as friends, which are made of other group members, or by the frequency with which the word 'we' is used as opposed to 'I'. A group will become cohesive under the following conditions;

Physical proximity, e.g. sharing an office;
similarity of background, values, interest;
rewarding experiences in the group, including success at tasks;
activities which require co-operation;
a skilled leader, who can preserve harmony;
the absence of hostile or disturbed personalities."

The people in the psychedelic community have come together due to a love of similarity of background and interest and the rewarding experiences within the group, e.g. attending music events with one another.

Here is a link to the e-book: The Psychology of Interpersonal Behaviour