Your ISP and VPN both could sell whatever data they have about you.
But there is a key difference: your ISP knows much more about you, usually. ISP knows your home physical location, almost certainly your name and phone number etc. But it’s pretty easy to sign up for a VPN while giving no ID, the only thing they care about is that your payment works. And most of them support paying via cash or gift card or Monero etc.
So usually it’s a win to split your data between ISP and VPN. ISP knows your home address and name etc and knows you’re using a VPN. VPN knows your home IP address and what destination IP addresses you talk to. Neither knows all the info.
Even with the VPN your data still goes via the ISP, they connect you to the VPN after all, it’s just that they can’t snoop. They could analyze the traffic pattern though and probably deduce if you are downloading something or streaming something.
Thats what I implied, yes.
Even if we assume there would be some civilian organised inspection, they could just be bribed. And IT systems are so complex, if they wanted to hide it, they could