That's pretty typical for how typography develops. Majuscule and miniscule letters were just two different styles of writing the same letter. But eventually, people started using majuscule (i.e uppercase) letters to give emphasis to the beginning of sentences or certain words, like names.

Italic typefaces were created by Italian type designers to mimic the cursive handwriting of the time. They weren't meant to be mixed with roman style typefaces. However, typesetters who had access to both roman and italic fonts started to use italic for emphasis when typesetting texts in roman type.

And of course blackletter is also just a style that originally tried to mimic earlier handwriting.