What you’re saying doesn’t make any sense to me.
Caches are there to prevent identical requests with identical results from being processed over and over again. Static files (HTML, CSS, JavaScript, images) are... static! They don’t require any processing, so they don’t need caching.
Both Nginx and the operating system are smart enough to keep frequently accessed resources in RAM. Saving these files in REDIS for later retrieval would just add complexity to the system.