> What people are searching for 

This is an extremely bad indicator for anything. What people search for does often not correlate to what they choose to use in their projects in the end. Take crypto/web3/blockchain for example. Lots of searches, but not many people who build a blockchain.

    > How many questions they’re asking on StackOverflow

Not necessarily a good indicator for popularity (although it will play a role). I'd say it's more of an indicator how much developers struggle with a particular language.

    > Developer surveys

Better, but even those have a strong bias based on their historic audience. StackOverflow is overrepresented with developers from 1-2 languages who have been historically the first/biggest community there.