In most cases a look back to the history of Digital Equipment Corporation comes to the conclusion that since the 1990s the company has made everything wrong and as a consequence DEC has declined. And indeed, DEC wasn't able to survive the upraising of the x86 computer and the former workstation and server products were integrated in today's HP company.
The more interesting question is why was in the 1980s DEC the number one in computing? They have made something right and sold their products to many satisfied customers. To understand the history we have to describe the divided market of computers in that period. On the low range, there was the upraising of homecomputers, for example Apple II, 286'er IBM PC, Commodore 64 and the Atari 2600 gaming console. In the midrange was DEC, and early Workstation vendors like Sun, and in the market for mainframe computers there was IBM.
The most interesting question is, why DECs customers have bought Unix based superminicomputers and not Amiga 500 and IBM PCs. Why was a VAX11-780 superior over a Commodore 64 computer? The purpose of the computers was different. Homecomputers were designed for playback existing software. The typical example was the Atari 2600 system which was able to run a ROM image which was sold separate. While DEC VAX computers were designed to create software and create CAD drawings. That means, the computer market was divided into entertainment where the software was delivered as ROM image created by publishing houses, and in contrast the DEC computers were sold to professional users who were programmers.
This distinction helps to compare the different software which were installed on the machines. Homecomputers like the Commodore 64 were equipped with a ROM kernel. Their main purpose was to provide a plattform which was able to playback existing games and applications. In contrast, Unix minicomputers and in the late 1980s also Unix workstations were designed as a programmer friendly environment which provided a shell, a compiler and a GUI interface.
The reason why professional customers and universities have bought the VAX computer was the need to use a computer as a programming device. The typical VAX user was interested in programming a scientific application in the C language, write a documentation with the troff formatting tool and send the project as E-Mail to a different university. The VAX computer was perfect for this task. And here comes the interesting point. Digital Equipment Corporation has become obsolete, the VAX hardware is useless for today's applications but the requirement of programming something in C, format a manual with a formatting language and communicate with other researchers are remain the same. This explains why today's homecomputers can be ignored by programmers. Apple, Microsoft or Nintendo have nothing to offer what is relevant for developers. The Nintendo Switch gaming console was designed well but it's the wrong choice, if somebody likes to learn Python programming. And the Microsoft 10 operating system is a wonderful platform for playback AAA game titles, but it is useless, if somebody likes to install a webserver.
Today's Linux is what DEC was in the 1980s: the number one platform for developers. It is equal to a fully functional operating system which includes multitasking and network capabilities and is used by 100% of all developers for realizing their projects.
Timeline of computing
Sometimes, a modern PC is presented as an extension of older PC which were build in the 1980s. But in a computer lab the transitation was different. In a computerlab, today's PC followed the former SUN workstation and the SUN systems has replaced the VAX11-780 system. That means, the processing speed and the operating system is constant over the last 40 years but the price has dropped and the size of the machine has become smaller.
Installing WIndows 10 on a PC of a computer lab is similar to installing MS-DOS on a DEC VAX machine. It makes no sense, because it doesn't fulfill the needs of the users. A computing lab has the obligation to teach students programming in C, not to teach them to buy software from the Microsoft store written by other.