Simula originated as a tool to do simulation, hence the name. It ended up as a general purpose language with some special features for simulation. Simula was bases upon Algol, and in effect extended that language with features for input/output, text processing and the revolutionary concept of classes.
In an article in ACM Sigplan notices Dahl and Nygaard tells about the development process. I have not been able to find the article, and may not be accurate in the following stories.
The development process was not always peaceful. There was a visitor to the institute where they worked who came to a secretary there and told her that there were two men fighting in front of the blackboard upstairs. She went out into the corridor and listened. Then she could tell him to relax. It is only Dahl and Nygaard working on Simula she told him.
The project was financed by one of the computer makers at that time. I think it was Univac. But the Simula compiler was sold twice. The research institute was negotiating for the purchase of a computer, and managed to get acceptance for delivery of the Simula compiler as part of the price. As the contract was finalised, someone higher up in the hierarchy came over and took part in the meeting. The price was already deducted from the purchase price, but someone (probably Nygaard) brought up the project anyway, and the visiting boss said - yes there was a deduction for that project.
Not all of the financial transactions around Simula were as successful. Some years later, after Dahl had become the first professor of informatics at the University of Oslo, Donald Knuth visited the institute. When he left, he wanted to bring a Simula compiler back to Stanford. The research institute that had the rights wanted payment for the compiler. Otherwise Simula might have been part of what students at Stanford University learnt from middle of the1970s.
On personal note - Simula was the 2nd language I met. The first huge improvement over Fortran I took note of, was the input/output system. Soon I discovered some of the beauty of classes. Later I had the fortune to have Dahl as Professor.