It was, actually, when gtalk, facebook, and whatsapp (thought I'm not completely sure about this, just have a reasonable suspicion) was using it in the background.

Then money people came, and destroyed it, then the idea of Matrix came, because of Slack, but thanks to people like Daniel Gultsch of https://conversations.im/ , XMPP is actually growing again. Slowly, but steadily: https://blog.prosody.im/2020-retrospective/