we both know damn well the next time L1 isn't "dead" nobody will solve anything and people will just migrate to altcoins. exactly like last time. and if L1 stays "dead" well there goes your security budget.
but that's the thing. this is how blockchains scale, naturally, all by themselves. a blockchain fills up and people just go to another blockchain. nobody has to write a blogpost or do a podcast or go to a conference and beg people to do this. people do this so much, it's massively popular. switching to altcoins is more popular than using lightning or cashu or any of that silly crap. this is what the market overwhelmingly chooses.
the sidechain idea is the only natural way to scale blockchains. instead of going to a different blockchain with a different currency, one currency can be multiple blockchains. you can ignore the ones you don't use, they can all have different features, and miners get paid for every single transaction. no need for altcoins ever again, and the security budget is finally solved.
you can do it with BIP300/BIP301, or it can also be done with covenant opcodes that are expressive enough. what you don't want to do is use a closed federation. that's retarded.