> Groovy has risen from #81 in July 2018 to #15 today

The rise to 15 is probably not correct but 81 is probably as inaccurate the other way as 15 is today. Given how ubiquitous gradle has become and groovy being the basis of that. Especially when you consider the nature of tiobe, it is about search results, so even people migrating away from groovy will generate "groovy" traffic as they try to figure out how to do equivalent things in, say, kotlin.