One of the main goals of Tari is Monero success. Fluffypony emphasized this in his latest presentation on Tari & Monero, which I strongly recommend to watch:
https://www.youtube.com/watch?v=zmeSSnppixYAdditionally, he did not leave Monero. He is still actively participating in Monero's development.
Kind of like one of the main goals of Ticketmaster is the US dollar's success? Please, it's a private company. I'm glad it exists but let's not get carried away.
Did you actually watch the presentation? Furthermore, Tari will be merge-mined with Monero. The bigger Monero's market cap, the more secure the chain will be (which thus benefits Tari).