Computers can search thru petabytes of data far faster than humans, they can react to programmed conditions faster than human reaction time.
What they cannot do, and likely never will be able to do, is intuitive reasoning.
Computers are vastly powerful calculators and massive self-searching filing cabinets, which can automatically execute pre-planned and configured actions.
They are not God, or even mere humans.
The better the programming, the greater their ability to simulate thinking. At what point does it become indistinct from thoughts out of nothing?
They don't need to be. All they need is enough data regarding human psychology and gullibility to convince humans that they are. Wouldn't be the first time in human history people bowed before false gods.
Its hard to get our level of intelligence and learning without a physical body moving and interacting in the real world, never really understanding certain physical concepts fully (or more fully).