I'm in no position to comment on that, unfortunately. Not sure if Andy's group has detailed why their first-take didn't come off apart from this terse note on GitHub which notes that building an autonomous-db is what they're main goal is (rather than a nvme-first db, which seems like a sub-goal):

> The Peloton project is dead. We have abandoned this repository and moved on to build a new DBMS. There are a several engineering techniques and designs that we learned from this first system on how to support autonomous operations that we are doing a much better job at implementing in the second system.

Here's their alleged unannounced second-take: https://github.com/cmu-db/terrier