Slitherine

I gifted my client state a large sum of money and several turns later they started giving me their regions. Is this just a coincidence?

It is related, but not directly related. A CS can relinquish regions which are mostly surrounded by his liege, if he likes you. And you made him like you by gifting money.
All is tied, and when it works, it feels 'natural'

Thanks, Pocus!