If it’s just Crunchyroll doing this, you can disable auto-play for it (or just disable it for all sites, IMO automatic playback of media is pretty annoying).
Another alternative is to use Auto Tab Discard, which automatically suspends tabs which are inactive after x seconds. This also helps save memory and CPU usage, and also greatly benefits laptop users. So if you tend to leave your browser open and have dozens of tabs in the background, I’d highly recommend getting this.