Good and evil.

Haven't you heard about Hindus, for example? In many pagan religions, statues are just like icons. Idols, images of gods – unfortunately, many icons have become idols. This angered many, and often entire movements arose in Christianity that denied the worship of icons (for example, iconoclasts in Byzantium or Protestants).

An amateur's perspective. Of course, they are similar – they are incomparably closer to each other than, for example, to Buddhism, but they are still very different.

It is not known for sure, of course, but most likely you and Ganymede are right. There is even an entire field in psychology – psychosomatics – that studies the influence of mental state (including faith) on health.