Long story short: I had a disaster of a building experience, including shoddy electrical workmanship. In the process of arranging proper CoC but there are a few things I want to understand around earth leakage.

On my DB I have two neutral connection bars, one comes straight from mains and other is sourced from the neutral from earth leakage (EL). Due to one of the electricians mislabeling the circuits everything was a mess, meaning that neutral was being taken from incorrect places for things like my geyser and pool pump.

Both my geyser and pool pump's neutral was coming from the non-EL neutral bar which caused the EL to trip. After them being moved to the EL neutral bar there's been no tripping. For my own education I'd like to understand why:

1. Did the pool pump and geyser cause EL to trip? Is it because L was coming from the EL but N was not?
2. It seems like my light circuits are coming from non-EL neutral bar - why not just put everything on EL? Is there a good reason to not connect it via EL?
3. For something like a pool pump, would it make more sense to have both L and N coming directly from the mains and then have a earth leakage at the pool pump's db?

Sorry if my weak attempt at terminology is hard to follow...