People at A want to move to B, because culture at A is bad and B seems good.
People at B want to move to C, because culture at B is bad and C seems good.
People at C want to move to D, because culture at C is bad and D seems good.
And finally
People at D want to move to A, because culture at D is bad and A seems good.
Includes everything from Google, Atlassian, PhonePe, Swiggy, Microsoft, Amazon and everyone.
People leave mainly because of their managers. Or people just want a reason to switch and get a hike. Or just want not to miss out on fomo at other companies.