Ask HN: How can one company manage make C#, Java, Go, Pascal compilers?

After being disappointed with the cross-platform UI abilities of .Net5 I started looking around and ended up with Delphi. During my search I came across a language called Oxygen that fascinates me. An Object Pascal on steroids. I looked at the company RemObjects and I was floored. They claim to maintain totally independent compilers for C#, Java, Swift, Go among others and keeps them tracking new changes. This seems like magic. How can they keep up? Anyone know more of the story The compilers are pricy bit wow. Is there some trick to it? https://www.elementscompiler.com/elements/default.aspx