Originally, the Pi was going to run Python directly, with a minimal OS underneath, much as early home computers ran embedded BASIC. But as development continued

Originally, the Pi was going to run Python directly, with a minimal OS underneath, much as early home computers ran embedded BASIC. But as development continued, it became clear that being a full Linux system was desirable. Since it was originally meant as a cheap computer for students, it was felt that Python would be a good choice for a beginner's language. So even though the Pi supports many programming languages, the emphasis on Python remains.