I made a couple of posts a few months ago that might help explain the previous structure:
https://steemit.com/steemit/@steemreports/steemreports-the-anatomy-of-steem-and-steemit
https://steemit.com/steemit/@steemreports/steemreport-the-new-anatomy-of-steemit

I think these changes kind of split the RPC Server into parts, which are each less resource intensive to run.