The only answer is that the big whales want it this way! I have high hopes for next year though, price manipulation is the real thing!
It is quite possible that big payers are cashing out early and making profits. they would be buying in 6k range and when it reaches a certain level they would be cashing out rather than holding it for long term which previously it could have happen. Due to which price is not rising easily above 8k.
I'm not sure whales are the main factor that made bitcoin having price less than $ 8000, this is a market condition related to regulations that reject the use of bitcoin. Continuous price reductions will make some investors sell bitcoins that they have, and that spreads to other investors, so they make the same decision to sell bitcoin even though they are in a loss. Indeed, whales does have control to make bitcoin prices rise and fall, but they will decide to sell and buy depending on the information that comes with cryptocurrency.