Removal from the repo is usually done when a plugin has unpatched security vulnerabilities and the developer isn’t responding (or at least responding quickly). Given that there is at least one known vulnerability that hasn’t been addressed and the developer rarely responds here and hasn’t updated the plugin for over a year, removal isn’t particularly surprising.
This was an incredibly well-crafted plugin, but I’ve had to stop using it on sites I support because it’s apparently become unsupported. Not too long ago the developer responded to a support request saying no updates have been made because none were necessary. That’s clearly not true, as now evidenced by the removal from the repo. It will be interesting to see if the developer now responds or if this is the end of the line for the plugin.