why dont people donate to the established agencies instead of running multiple lundraisers?

Because some people might have direct way to help. If you are from a particualr place from gorkha and if u have the fund then would b the best one to help there coz u know what happenienf there.
and the well established agencies already have money. SOme finds are stuck at aiprot fo these agencies. So stip bitching.

It doesn't matter, let it be. All of the funds are getting raised for the same cause - you do what you can and want, don't waste energy by unnecessarily criticizing what others are doing.