A U of T linguistics professor explains all.

I enjoyed that explanation and it’s interesting to compare regional accents.  For instance, some north eastern English accents as well as the Stoke-on-Trent accents - among others most likely - still pronounce “you” as “yow” which is apparently the pronunciation of hundreds of years ago.

The shift was not as strong the further north you go.

I loved the explanation of the vowel differences between “though” and “thought”. One went through the vowel shift and the other didn’t.