Ive always been very interested in APIs. Watching SOAP fizzle out and REST take over was quite exciting. Now we even have GraphQL. But in 2010 I wrote a patch to fix Services module in the 2.x branch.
Eventually I became a co-maintainer and I immediately began to think about what 3.x would look like Hugo Wetterburg laid the ground work for this 3.x branch and I made the next several commits.
This set in motion the next 7 years of my life. Managing the 6.x-2.x, 6.x-3.x, 7x-3.x, and eventually 8.x-4x was a very time consuming task. As a full blown open source contributor I was having a lot of fun.
Services still lives on in Drupal 8 even though REST is built into core, it just takes a different stance than Drupal core does in how you define API's via code.