Do you think there are some sinister agenda behind this or is this just Bitcoin whales doing their normal thing?
There is no other hidden agenda behind their actions. Those who have the ability to manipulate market now do so because it is the normal thing they are doing to gain massive profits from crypto(in this case bitcoin).
no institution manipulates the price.
It is too early to say that institutions are not participating in the current manipulation of bitcoin price(because they like having control over things).