I disagree with your ideas about bitcoin tied with dollar or usdt as back up, its wrong assumptions because bitcoin have dependent currency without tied with any community or government such as dollar.
Bitcoin is a decentralized currency due to which no country's government can control it. But dollar or fiat currency has centralized owner to control it whereas Bitcoin does not. Moreover, Bitcoin has a fixed supply with no human hands and no scope of regulation, making it an independent currency. And for that reason there is no connection between USD and Bitcoin rather Bitcoin is a cryptocurrencies, but USD is a stable currency.
This special thing with bitcoin without controlling by any countries yet and keep dependent regarding with how many investors are holding bitcoin, talking about profitable bitcoin have more benefit than dollar who increasing values very slowly and depend their situation good or not. Right now many countries have against with dollar and some of them try to build up their own currency for foreign transactions where usually using dollar and right now they want use their own currency.