It’s simply a business and like any other business it should make decisions based on whats good for their people and their product. There is no golden “all startups should use X programming language”-rule.
(Good) investment money (if that’s what you’re after) comes from firms who see the quality of your product, not the language of the code it’s written in.
If you're in finance, there's a good chance you're using Java, C++.
If you're building a web-app, it's probably javascript/node, and likely moving to Typescript
AI? I whole lot of python.
So I'd take a look at what area you're interested in working in, and then make sure you're familiar with the language and tools which best fit that interest.
You must pick technology that solves your immediate problems or else you probably won’t have a product or a company.
If there are startups you’d like to emulate, just look at their job ads, they’ll say exactly what tech they’re using.
For me I picked a language and framework that I’m most productive in and stuff that’s liked by the people I want to hire.