Grammar Question: Remain vs. Remains

OK. But this is GQ. Why are people replying if they have no understanding of linguistics? This wasn’t a question about what would sound more natural, but what is correct.

You do realise this is a linguistics question, yes, not a question about economics?

The part that talks about the partnerships is in a separate, embedded clause. You don’t need to overthink things - who is important, how many partnerships are there? That’s philosophy. Just break it down. Look at the actual words and how they function.