Actually cryptocurrency is not a threat to traditional bank but traditional banks see Bitcoin as threat reason been that imagine now 2022 you kept $20,000 in your bank account how much interest I will bring and you bought Bitcoin worth $20,000 in 2022 how much interest you will make by now
So traditional banks use our saved money for other businesses since we keep our money in Bitcoin to give huge profits over the year so the traditional bank sees bitcoin as threat
You conclusion is correct but the reasoning is wrong. A certain bulk of bitcoin bought back in time is worth more that the buying price is not the reason why banks dont like bitcoin.
Banks are centralized and they are censorship prone, while bitcoin is not so. This is why banks dont want people to invest in bitcoin. But it is also true that without the banks you will face monetary problems depending on where you live because living on crypto is not complete yet.
The trading profit from bitcoin is not be considered here - indeed it does give much returns in that but that was never its main purpose.