If he effectively dropped the idea of Divine Law I do not understand how he is the king and how his son and grandson are heirs to the throne
Parliament decided it.
Charles I civil war - we ended up a republic that slipped into dictatorship with Oliver Cromwell who then tried to pass position on to eldest son who didn't have support- parliament ended up asking Charles II back - I think he agreed to run things past parliament - so we had the The Restoration.
King brother was heir as Charles had no children in his marriage - James II had two daughters first wife - eldest Mary married to cousin Duke of Orange next in line after them child of their eldest sister. Jame II married again had son and converted to Catholicism - we had The Glorious Revolution - William invited to take over - so got William and Mary.
Then we ran out of Stuarts - Ann being last no heirs - Queen Anne was the last monarch to withhold Royal Assent.
Then parliament went heir shopping - creating The Act of Settlement in 1701.
So now to inherit the crown you need to be a legitimate descendent of Sophia of Hanover and protestant.
George I who got it was 52nd in line to the throne. We passed over a lot of Catholics but Sophia was second youngest of large family of mostly I think protestants - she got it due to political considerations due to Hanover being useful and William apparently grew up with Sophia and she saw him after he lost Mary his wife and offered comfort.
Constitutional monarchy developed under Hanoverian - their last monarch was Queen Victoria.
Elizabeth II parliament change act of succession to stop putting boys first after a certain date - so affecting no one place currently alive at the time.
Royal powers are murky - the monarchs head of arm forces and head of state often can't use what they have or they will lose them - but they have technically more than many people think and seem to have a lot of influenced behind the scenes.
I not sure most people are wild about having a royal family - but our system proven a stable system over a prolonged time period - they've generally proved smart enough to wrap themselves in patriotism and good works - we are not the only constitutional monarchy out there - and getting rid of fairly benign legacy system just isn't worth money effort and potential pitfalls - yet.