As far as I can see, Tent unfortunately seems to be inactive. Last commit in 2013: https://github.com/tent/tentd, last blog post 2014: https://tent.io/blog

so we have a failed protocol from 4 years ago, what makes this remotestorage more likely to succeed?

Tent's goals sound similar on the frontpage, but are actually very different. It's more of a communication protocol than a a data storage one. This page is slightly more informative, albeit not much: https://tent.io/about

Tent is built around posts. Each Tent server stores a single user’s posts and sends copies to the user’s subscribers.

I seem to recall that tent - the protocol - used to be an effort for decentralized social networks...though I've lost interest years ago...so not sure what is happening recently, or if they've pivoted to different space.