* Venmo launched the first out of all the systems you mentioned
* Venmo was one of the few (maybe only) system that allows you to pay users who are not on their system. Say you need to pay Joe and you were a Venmo user but Joe wasn't. You could still "pay" them on venmo and they would get a text back saying if they signed up they would get the payment. No one else did this well when they launched
* Venmo integrated with facebook so many of the people I needed to pay were already in the system
* Venmo was the first free system to use
* Venmo was the first mobile friendly system to use. It was the first major system where I could split the bill real time at a restaurant
* Venmo paid early adopters to join (I think I received $2 to make my first payment)
It seems like a clear case of first mover advantage. I'm sure the systems you mentioned are now better, but at the time Venmo had the best UX and now that everyone I need to pay is on it, why would I switch? The few cents of interest loss I lose every year isn't worth finding out if everyone I need to pay is on one of the alternative systems.