This is probably linked to exercism.io proposing a challenge: learn a subset of these mechanical languages challenge with Nim being in there.
People are doing a lot of Google queries to learn the language, thus making our position in the TIOBE index climb. When we know Nim, it is unuseful to look things up (unless through our Nim Manual's bookmarked page). We have also a scarce presence on Stack Overflow. This ranking supports better old languages that people will look up through search engines queries. It is completely irrelevant today. Just forget about it. Fortran is not that much old. I know plenty of researchers that uses Fortran due to its parallelism features and HPC libraries.
