4 pair of cables lead to Ceiling fan box
You have a switch loop here

The white wire bundled in with the blacks along with the solo black wire are telltale signs of an old-style switch loop run using /2 cable from the fixture to the switch(es), with the white wire as the always hot and the black as the switched hot in your case. So, with the power off at the breaker:


Use a wrap of black electrical tape to mark the white wire nutted in with the blacks as a hot wire
Nut the ceiling fan black and blue (or just the black, if you don't have a light kit on your fan) wires to the lone black wire
Nut the ceiling fan white wire to the existing bundle of entirely white wires
And nut the ceiling fan green wire to the existing bundle of bare wires.