When I forget to sign in to YouTube, I see the same pattern, shitty ads that are clearly only allowed because otherwise YouTube wouldn't have sufficient ad inventory to meet their internal KPIs.
The reality is, of course, that Google and its ilk doesn't give a single rat's ass about people falling from scams or getting infected by malware. Scams and malware pays better than "ethical" ads (to the degree that such a thing exists). It's a travesty that there are apparently no laws against their behavior.
In the USA I’m pretty sure advertising scams - even the more ‘benign’ ones like claiming a product does something it doesn’t do or lying about its efficiency - are illegal. There’s just no - or not nearly enough - enforcement.
The cost of enforcement would break every government's budget. The cost asymmetry is the problem.