I am not open to your ahistorical take on Google Chat and XMPP.

Google didn't do anything wrong by using an open standard.

They didn't do anything wrong by building a good interface that people liked to use.

And they didn't do anything wrong by disconnecting from the network when the spam and harassment outweighed the benefit to their users.

We, the XMPP community, failed to capitalize on success by diversifying the network. It's our own fault not enough nodes were there.

If you'd like to draw some conclusions about ActivityPub from this, it should not be that a network should disallow supernodes, but that we have to counterbalance them with a wide diversity of other nodes of different sizes with different value propositions.
That huge audience of GChat users was an immense asset, and we fumbled it.
@evan Absolutely, if anything it should always be an opportunity to learn and grow the platforms that we create, build, manage.