I’d like to correct a common mistake: Islam usually didn’t force people to convert.
Christians and Jews were free to convert but pagans were absolutly forced to convert. Another thing is that like other invaders, locals were forced to pay annual duty and it varied from ruler to rules. Those who couldnt pay for whatever reason could only choose between death and conversion. Muslims were also forced to remain Muslim or die.
so while not everyone was forced, a lot were
Christians and Jews were free to convert but pagans were absolutly forced to convert.
That also happened, but I’m pretty sure most of the time dhimmi rulings were adopted. That’s why, say, Zoroastrians got to stay Zoroastrian.