Just because a programming language is popular, doesn't mean there is much written in it. A lot of studies of 'most popular' are done by just looking at common code repositories (Usually github or Sourceforge) and checking the extensions of the files (Some are even lazier than that and just look at project tags). Such studies rarely consider such factors as lines-of-code, activity, etc.
For every Linux Kernel, you have hundreds of trivial projects written in simple languages, many by CompSci students as a term project.
The problem remain as long as we human stay obsessed with tacking numbers onto things that can't be easily quantified. Like, do you count the popularity of a programming language by number total software projects that use it? Lines of code? Number of contributions? Download count? Installation count? Execution count? Number of cycles the code has used globally? Or do you go with something based on humans and ask everyone what their favorite language is? Which one they use most often? Or even some subjective factor like what language is most important to humanity?