As far as I know most, if not all, of these scams have been perpetrated against the elderly. All operations (authentication, signing) can be initiated remotely with just a personal ID number, so the typical scam meant calling up someone and claiming that "an authentication must be performed", and simultanously initiating a bank login session. If you can keep the victim on the phone and using the BankID app when you tell them, you could basically login and empty their bank accounts. This has been largely fixed using QR codes to initiate login requests for major internet banks (which means you have to be in front of the same screen now) and other clever workarounds. But it has also always been a fact that there will be a description saying what you are signing, in the app, so being careful you could easily avoid being scammed.
I think its largely a great asset (BankID) but its never gonna be 100% tamper-proof without being seriously neutered.
The same NemID is also used to file your taxes, look at all your health info, get married, everything basically.
Credit card payments are much lower security level, and they're basically forcing sharing credentials amongst all the sites you pay on.
And I believe you can also use sms + password for online transactions.
I don't think it's good that users are taught to accept their primary citizen 2FA on any random website and app where the URL doesn't even show.
We didn't need to scam anyone though, just have them verify that they were a Swedish resident (had a valid Swedish SSN and we're the ones ordering) :D
Its the ID method I use for credits, pharmacies, health care, taxes, but was apparently not an ID so it's not id-hijacking.
Klarna has man in the middled my bank account before and performed a purchase and I've boycotting any company having them as the only payment option since.
OH, now I also remember Klarna adding credit in my name since they only needed my tax registered adress. I lived in a dorm so someone just used our public information to take out credits to order sneakers and could break into the crappy entry mailbox.