The idea is fractional reserve banking is that the loans are at least good enough in aggregate in normal course to cover its liabilities. Of course there are black swan events (https://www.investopedia.com/terms/b/blackswan.asp) that are so far out of expected that banks fail anyways, or the banks are incompetent and make things like sub-prime mortgages (https://en.wikipedia.org/wiki/Subprime_mortgage_crisis) that tend to fail all at a once.

Yes, I understand that, I just don’t see this bitfinex situation much different from what is generally accepted as normal in banking sector.

A loan is an asset, it just isn't a riskless one. A great example are bonds, typically considered to be assets, which are technically a loan that you have given to a government or company.