How do you decide a tech stack to build your project?

Lets say, you want to build a project and you have to decide the best tech stack that is suitable for the project. I often cannot understand why some companies favour a tech stack over another? One of the most common reasons I hear is thats what the initial devs knew and they just built it, but what are some other factors to consider while picking the tech stack. Would be great if you had some real life examples to share!