Comment by userulluipeste

"I think it's all just normal evolution of language."

The normal way for languages to evolve is for words to spread into different (adjacent) forms in order to express more nuances of their original meaning(s). The collapse of words' meanings, and for basic things as (nominative case) pronouns no less, like it happened in English for "thou" and "you", is not fitting the definition of "normal" in the larger context of linguistics domain.