The original Mando’ade were the Taung an alien species who invented the culture. The new show also introduced the idea of foundlings. One more thing Jango Fett was adopted by mandalorians (Jaster Mereel I believe) when his parents were killed. Making him a foundling himself. Raised into the ways of the mando’ade under jaster’s guidance. Jaster being Mand’alor. The dent had to be the fact that beskar wasnt even a thought in anyone’s mind when ROTJ came out.