ISPs can monitor what you're browsing through DNS requests and SNI host headers and sell that data to advertisers who then inject personalized ads into ad supported websites.
The thing I don't get is why they need a spyware router in everyone's home. They own the infrastructure and know where all the traffic is coming from. They can do this with their own hardware outside people's homes.
I do wonder if they're sucking up LAN traffic data too, though, some of it which might be unencrypted, like smart devices talking to each other.
