You can buy a plot of land and start planting crops. You may want to build some structure and make changes on the land. You start a new business. Then you may hire farmers to take care of your land and make it grow.
The same is valid for the game as a service business. Often the people who start a game are not the people who make it grow. Often you need a certain type of people to find something new, a new land. But then you may want expert farmers to make it grow.
It’s not that people cannot do both, it’s a matter of will. Creating a brand-new experience requires the ability to spot opportunities and connect the dots. Maintaining and making a game grow requires analytical skills, instead.
Someone says that one thing is to go 0-to-1, and another 1-to-1000.