historically, what made relational databases popular?

Question

EDIT I\'ve just started skimming Codd\'s famous 1970 paper that started it all, that Oracle was based on (A Relational Model of Data for Large Shared Data Banks [pdf]),

Answer 1

For the same reason why the script languages are popular.

You can make a query with your favorite text editor and just issue it, without bothering about the actual physical schema.

It's not the fastest model, not the most reliable model — it's just the most productive model. You can write ten times as many queries in an hour.

You may want to read this article in my blog which compares the most popular database models:

• What is a relational database?