Simplicity of the tool - it was esy peasy!
At my last company, I had to build a performance-sensitive, multimedia processing pipeline. Javascript or any interpreted language (despite the JIT) didn't make the cut. I need the speed of a language like C but the maintainability of JS.
I found Reason. Esy let me install my C and Reason deps reliably and intuitively. It was constantly and in development, and where it lacked in features, it made up for in reliability and welcoming community. Using it meant actively involved in its development, which was a pleasant experience as the maintainers, Andrey Popp, was very welcoming. It was a great learning experience. My time spent on the project gained me a lot more things that I gave back, I believe. Thanks, Andrey!