Why do the military elites use different CQC systems?

Question

The SEALs use a CQC system that is based on JKD (R.A.T.), the DELTAs one that is based on BJJ, and the IDF special forces one that is based on Krav Maga - why the differences in the CQC techniques the military elites utilize?

Answer 1

different opposition units, different equipment, different training

Answer 2

If you've ever trained in martial arts of been to any shooting schools you'll notice that everyone thinks their ideas are the best and most high speed, low drag.  Plus the ego factor