Most vertical market solutions were started by advanced end users trying to solve their own day-to-day problems. Chances are they couldn't afford to hire a team of developers to build them a custom solution, so they cobbled one together themselves. Other people in their field see what they're doing, get excited, and a lightbulb goes off - "I can make a business out of this!".
Eventually it gets to the point where those solutions need to start following the rigors of a proper dev shop, but in the early days, it's more often than not the "low code" dev that you're talking about.
Most vertical market solutions were started by advanced end users trying to solve their own day-to-day problems. Chances are they couldn't afford to hire a team of developers to build them a custom solution, so they cobbled one together themselves. Other people in their field see what they're doing, get excited, and a lightbulb goes off - "I can make a business out of this!".
Eventually it gets to the point where those solutions need to start following the rigors of a proper dev shop, but in the early days, it's more often than not the "low code" dev that you're talking about.