When you build, launch, and grow an online business what ends up happening is you get organic traffic visiting your product. I'm talking about people Googling around and ending up on your website.
And as you go about running your online business, you'll start to realize that there are many, many problems within your own business that can be solved by another product. If (when) you get the bright idea of building that other thing, you can use your previous success from a traffic perspective to funnel people to your new product.
Repeat this as many times as you like.
I call this Traffic Stacking. Each successful product you build and grow becomes a starting point for more products you build.