There was a few different ways to achieve bigger payloads. One was by initiating some handshake for a different protocol. But the keysend like one, we used AMP to essentially be a MPP-like keysend payment where each part had different bytes and it either all made it to the recipient or none at all. Added atomicity to the data payload.

If you're just sending out a bunch of keysends, you have to consider the fact that one might not make it or ever make it. You wasted sats for a broken payload if the rest made it.