But what I don't get or understand is that if I expect Hive go down and BTC go up how does the ratio hive/BTC keeps stable?
My explanation to this is: if BTC goes up, traders will want to chase it and buy more, hence spending HIVE to accumulate BTC, sending the HIVE price down. I don't know if that answers your question, or even if I understood your question correctly, but that's the general mechanism between BTC and alts, not only HIVE. It's an inverse correlation resembling a hate-love relationship.