Orbi RBK50 Connection Questions & Backhaul Setup with Telstra Velocity

Hi everyone, I have a few questions with regards to a new Orbi setup: 

- Telstra Velocity FTTP connection, similar to NBN

- FTTP box is downstairs, along with a switch for 3 ethernet ports to the remainder of the house. 

- 1x Ethernet to the living room

- 1x Ethernet to upstairs

- 1x Ethernet to who knows 

I am trying to have the Router downstairs to replace my old TGateway Modem, and the satellite upstairs to pug in 2x Desktops via ethernet. 

I have setup the modem, and plugged in the ethernet cable which routes upstairs. The satellite is plugged in via the upstairs ethernet port, and the PC's have been subsequently plugged in also. 

My question are: 
1) Now that I've configured the backhaul (I think?) to upstairs, the WIFI has turned off from the modem downstairs, why? 

2) The Satellite upstairs is now acting as the primary WIFI router, and an ethernet distributor, why? 


My end goall: 

- 1x Modem / Router downstairs which delivers Wifi Signal, and ethernet to the ports plugged in, one of which goes upstairs. 
- 1x Router / Satellite plugged in via ethernet upstairs which delivers WIFI signal, and 2x ethernet connections to Desktop PC's. 

Happy to answer any questions, bit of a rookie here and mainly self-taught :)