It made sense throughout the whole stack. We're right on the edge of small-midsized, so we need to find technologies which our people know or can easily learn.
Database level, our DBAs are very SQL Server oriented and all of our primary data stores are such, the ORM for .NET Core, Entity Framework plays very well with it. This was probably the biggest factor. It has a decent Redis library.
Application Level, it is a managed runtime, strongly typed, performant, with a strong ecosystem of libraries. We're running calculations on data so out of the box performance is important. Scaffolding models into Controllers and Views is handled very well, along with migrations. Strong facilities for serializing and parsing Json & XML. Nice interfaces for integrating email and SMS services. It has a secure, extensible authorization framework (Identity Server). It has a strong debugger, when you make a typo, you know right away, so you can cut out the vast majority of issues by the time you're running it. Easily share class libraries across projects with a private NuGet repository. A nice implementation to get metadata in System.Reflection along with intuitive handling of generics. Support for lambda expressions and functionalish behaviors. Carefully considered implementations of asynchrony and parallelism.
For front-end tools I'm not as up to speed, but browsersync is built in, so that is running without any configuration. They have automatic minification of css and javascript on build, and some tools to work with Angular, Vue, React, etc. as well as an emmet clone which allows you to use emmet shorthand when generating html.
Dev Ops, the Visual Studio IDE is really comfortable for a wide range of people. Strong integration with GitHub & Docker.