I'd argue that it has no negative feedback mechanism. More security isn't always useful. There's a reason you don't wear 25 seatbelts in a car or drive a tank to work. At some point more security is ineffective, and then eventually detrimental.
Yes, more energy is more security in this case - which of course you can obtain in alternative ways. But so is driving a tank. So is living in bubble wrap in a missile silo in the middle of an open field. We don't do those things, though, because we have negative feedback mechanisms. Bitcoin does these things (analogous versions) because it doesn't.
And as for why it's failed as an L1, it set out to be a digital cash. 2-3tx/sec isn't enough to support a mid-sized Costco or a flea market let alone a global currency. 1 transaction per person on earth today would take over 75 years and cost 1/3 of a trillion dollars, and 100% of the remaining block reward. It's like a soviet-era phone line - better put in your order early, I guess.