It's that the web interface, and process for starting a "droplet", is dead-simple and super-elegant, their support docs are comprehensive and easy to use, and they even do things like let you manage your own DNS records. And it all just works.
Digital Ocean is 100x easier and quicker to use than AWS, without exaggeration. It's easy to start a hosting provider -- it's really hard to make one that is also really high quality, intuitive and easy to use, and then cheap on top of it.
I've used Digital Ocean for a couple of years for small personal things, I'm actually currently in the process of moving a bigger site from AWS to Digital Ocean, at this point it's turning into a no-brainer.