By doing something like this, it would prove their self-governance to be incompetent and completely irrational.
You don’t prove good governance by making your league a laughing stock, very publicly bullying a whipping boy, and throw around ridiculous charges and rulings like it’s a banana republic.
Everyone is also acutely aware that actual countries own football clubs now and that the current champions have literally, inarguably bought their success over a sustained period of time, and that they’re lawyers are currently obfuscating due process.
The initial 10 point deduction was met with ridicule in the national media. Any additional investigations and punishment would shine a much brighter spotlight on the Premier League’s conduct, which would be massively self-defeating.