The problems you have to solve in a startup - finding a product - market fit, with sufficient customers and sales and marketing economics to breakeven, and even grow using reinvested earnings. You at pioneering markets which by definition is uncertain and small
Once your company is self sustaining the problems are different: you know who your customers are, so you can go ask them what other products they might want to buy. Or you know your products you are already making and now you can look for prospects similar to your existing customers that you might sell to as well to grow your market. Only in this way do small markets become large
These skill sets are very different, so much so that many successful entrepreneurs will leave their successful startup and become serial entrepreneurs and few large firms are run by founders for their whole existence.
An entrepreneur can generally notice that the scale of the company limits their personal impact and the kinds of problems have shifted and they need to shift from visionary to empowering leader who manages people who are experienced in growing market share.
When that happens you have to decide what yo love more, the tasks you became good at or the company that resulted. If you are more of a serial entrepreneur at heart this is the moment where you feel like a parent struggling with whether your baby has grown wise enough to make it on its own. Every parent of adult children knows how those questions never have obvious answers in the short run, but you make guesses and see how things turn out. Entrepreneurs experience the same thing.