How do major changes in the written/spoken language come about?

For instance, people used to say ';I be....'; or ';She be...';



How did that get changed to ';I am...'; and ';She is...';?



I have other examples, but that's what I came up with first. I'm intrigued to figure out how such a change would come about.How do major changes in the written/spoken language come about?
By overusing the incorrect version, it becomes the ';accepted'; one.



Personally, I balk at such things, but then, I'm only ONE person!





Have a Grammatically Correct day!How do major changes in the written/spoken language come about?
The english language has gotten many influences and that's why words or sayings change through time.
Well my guess is that, as soon as a phrase becomes popular among the population orally, they somehow become accepted by the society and end up in the dictionary