There was really no reason to do so at all - it's an ordinary company building an ordinary application. But some CTO or dev lead years ago thought it important to use whatever the fancy tech of the day was to build a fairly ordinary business application.
But now they have trouble hiring people because there's a tiny pool of people who know that language. And it is years down the track and all their technology is built with whatever that language/framework is - too expensive to easily bail out, but probably necessary anyway.
In 2023 you've got to have really good reasons for not using C#, or Java, or Python, or TypeScript for building your web project. Maybe Golang - it's getting some good traction in the DevOps space.
If you make decisions about technologies and this latest thing appeals to you - maybe use it for your personal projects. The CEO has employed you to make responsible decisions not play toys.