First, the people in these meetings are already coming with high expectancy - they want it to be God. Second, you need to create the right atmosphere - hence the long periods of singing certain types of songs to make people feel relaxed and warm. This creates a far more mystical atmosphere. Songs full of Christian or Biblical doctrine work against people suspending their critical faculties. The effect is to create a mindlessness that will open your audience up to suggestion.
Most people have no idea just how powerful suggestion can be.
Let me add that all this is not necessarily done wilfully by leaders. This is something many of them have stumbled upon. No, not at all. If you do not believe that it is God that is doing these things in the meeting, there is no way you will fall down. But remember, I am the one running the show.