[intended]

Not the full picture.

You can have self selected individuals working on an interest who integrate and form a community.

My favorite example is the bay12forum for Dwarf fortress.

High barriers to entry, you need to actually be highly engaged to get over the interface - means that entrants to the forum (used to) stick around and get to know each other.

What you are seeing is the difficulty of paying matching costs for complex types of matches.

In the old system you didn't have options, so shopping around didn't make sense.

In the new system you do have options, so shopping around becomes more attractive.