The TIOBE Index [1] ranks Fortran at 12th place! Consider that Ruby is at 18th. In my opinion, this says a lot about the value of the index.
Still interesting to see that languages like Fortran (12th) and Pascal (13th) are ranked higher than the most popular languages for mobile app development (Swift for iOS, ranked 16th, and Kotlin for Android, ranked 17th) or a highly praised and adopted language for new projects like Rust (only 19th!).
If you want something more reasoned there's this: https://blog.nindalf.com/posts/stop-citing-tiobe/
Are you a non-technical manager? Then hire people who know the language your company has always used, or otherwise whatever languages your hiring pool is familiar with.
Are you a technical manager? Then you evaluate languages based on the intersection of hiring availability and technical merits.
Are you a student? Then use whatever language looks most interesting.
Are you an educator? Then use whatever language best expresses the concepts of the specific curriculum.
Are you an open source contributor? Then select a language to work in based on technical merits, personal taste, and community interaction.
"Popularity" is not one thing, it's dozens of things which all vary based on context.