Since JPMorgan is lending against Bitcoin by keeping it as collateral, JPMorgan's decision may be a relief for Bitcoin holders.
Because there are many people who are constantly hoarding Bitcoin but sometimes they need a large amount of money that cannot be covered by their emergency fund. Then, Bitcoin investors are forced to sell their Bitcoins.
JPMorgan's lending against Bitcoin may keep the Bitcoins of such Bitcoin investors safe.
If they ever need an amount of money that their emergency fund cannot cover, instead of selling Bitcoin, they can take a loan from JPMorgan against it and repay those loans by earning money later.
Also, when Bitcoin comes to DIP, even if they do not have enough funds to invest, they can enrich their portfolio by borrowing from JPMorgan aggressively by buying Bitcoin.
you also forgot the main advantage
loans are not taxible
so giving coin to JP and they give you cash(as loan) is not hit by cap/income tax
if you dont repay loan, they keep the coin, which on your end is like selling the coin (coin->cash) but the tax man end is tax free (loan->collateral default)
(this is not financial advice speak to a financial specialist to understand full details)
They are thinking about negative things while there's advantage on what JP Morgan company is doing. We could see that this big institution are now slowly adapting on the changes and think about adding Bitcoin.
Since if they got feared about their Bitcoin will be seized by them they better pay what they loan so that they won't get a problem from the institution.
Also what's good development happened is JP Morgan bank is now allowing their clients to buy Bitcoin which is good development happening in the scene
Although they are still skeptic but at least they are doing good step for allowing people to do this transaction on their bank.