I’m not quite sure what you mean by the ‘spirituality’ of the group. But for sure, massive meetings focused on a specific theme, do increase spirituality.  When like minds come together to discuss issues which are uplifting in nature, individual energy levels rise, which in turn increases individual vibration levels and connection with their higher selves and infinite intelligence.

The result is feelings of what is called ‘being in the zone’. Euphoria, excitement and passion come alive and can often be witnessed by the tone of voice, body language and expressions. Everything else is forgotten in the moment and the focus is on the topic of the discussion.

There is also a shared energetic connection as the co-creation and unity contribute to a shared universal consciousness which has the potential to bring into manifested form the theme of the discussion.

This can, however, work the same way if the topic is negative in nature. Whilst the discussion is negatively orientated it has the same positive effect in that it is a shared co-created experience with the potential to manifest and contribute to the universal shared consciousness.  Thereby expanding all that is.  So yes, massive meetings increase spirituality.