also, if you step back, Ruby's problem is it consists of a fading community of millenials and Gen Xers who first came to Rails when it was the best/coolest option. however with the majority of builders now turning to JS for web, Rust (and Go) for systems, and Python for ML, it doesn't have a use case anymore that can drive a community or any hope for growth in the future. so a "niche DSL" for legacy webapps and plugin systems is what's left IMO, but i'm sorry for being super frank about it
languages like this with a shrinking community and loose security policies pose around the centralized package management system pose high security risks to its users.
Also, commit access to Github doesn't even say anything about access to deploying the actual package on rubygems. If security really was the goal, there were a million less invasive ways to make this change then revoking commit access from the active maintainers. Set up branch protections, require approvals, etc. There are a lot more tools in the toolbox other than "remove all of the maintainers".