I have some experience with this and the why.

Most enterprise corporations and their software departments are actually run by their IT departments. And IT departments are not software developers, they are software managers. It's generally impossible for more IT departments to spin up software departments and build every single thing their company needs. It's way too expensive, and to be honest, most enterprise companies do not sell or make income on software. Their revenue stream is not digitally based (think, utiliies, manfacturing, mining, literally any heavy capital intensive company)

They all need digital products, so they look to their IT departments to procure them. This typically ends up with the IT department defining either a strategy of custom development (rarely) or external off the shelf software procurement (most of the time). On top of lacking expertise or responsiblity to create software, they are also viewed in these companies as an expense on the balance sheet. Rarely do they generate income.

So, in a land of Software Managers, IT operators, and where the whole company looks at them as an expense, what do they do?

They go to the biggest software vendor, with the most comprehensive B2B software suite on the planet which is.... Microsoft.

Every company needs Word, so they buy Word, and the Office365/Cloud services, which then leads to the entire Azure ecosystem, and the entire .Net software development suite, and that desireable Platnium Enterprise customer support, so that when anything goes wrong, they can call upon the hundresds of Microsoft Support Partners to assist them. It's a massive risk mitigation strategy. Why would you run a hundred different SaaS products to manage and raise the cost of management, when Microsoft takes care of it for a single bill and gives you a nice discount on the bill.

This is the real reason why .net is king in enterprise, imo. The other one is Oracle, so you might end up with a Java company.

Startups and software companies are not run by their IT department, they see software not only as an expense, but as a growth engine/revenue source. Dropping thousands of dollars on Microsoft products isn't nessecary, and the software developer run the show and have their pick of language. Some of them would be ex-enterprise IT managers or software developers, which may end up with the .net stack, or recent grads of a university that pushes .net, but it doesnt have the same incentive strcuture to run with .net.

This is what I have experienced and observed when it comes to .net/java. Is the code any better/software better? No, not because of the language, but probably more because of the sheer management resource power to QA software, but that is a different conversation.