They were changing when the printing press solidified English spelling around that time, which was also a period when the pronunciation of vowels were changing.

Which is the main reason English pronunciation is so weird.

The reason the spelling is so weird, is the people running the first English printing presses were almost exclusively Dutch, had a very loose grasp on the English language, and didn't really seem to give a fuck how accurate they were.

If they thought something should be spelled differently (usually more Dutch) they'd just change shit.

In a lot of ways, English isn't even a "real" language, it's more of pidgin language