There is no myth. I'm not sure why anyone would think starting a company would be passive for very long. Even if you're successful and generate revenue, hire employees, and take market share, someone still has to provide leadership. And even if you manage to become some sort of absentee shareholder and the company is run by others, you still will be worried all the time about the golden goose turning to crap.
There are 100 podcasts about passive income. Do X then sit on a beach and cash checks. Total scam but people want to believe. When told what you want to hear, some people will listen.