I seem to remember (but I can't find the source) that Wirth initially had three aims in designing Pascal:

1. To use it in teaching a structure programming course to new students. As in the late 60's all student programming was batch mode (submit your program to an operator to run, and pick up the printout the following day), this meant the compiler had to be single-pass and give good error messages.

2. To use it in teaching a data structures course involving new data structures worked out by Wirth and Hoare.

3. To use it in teaching a compilers course. This meant the compiler code had to be clean and understandable. Being single-pass helped in this.