Then in the original project you can say “the last version of this project is N.N; here are some possible candidate successor forks, which have not been vetted”.
This way no one who is merely keeping up with version numbers will accidentally step off of a reasonably good package on to a fraudulent package.
To prescribe some preventative advice based on this: it's probably not a good idea if your project gets popular to continue being a solo developer in open source. So plan ahead based on your popularity.
And your project isn't likely to explode in popularity over-night and be a dependency for 1000+ other projects, so you should be able to see this coming.
Of course, this is super-easy to prescribe in hindsight.
They are practicing resume driven development. While this is unpaid, it's not completely altruistic.