Mark was adopted by the English?

Mark was Scottish, and born in a time when the Scottish were a threat to the English. Prior to his birth, the King of England had a brief spell of paranoia and asked if all the first borns in Britain be killed, because at some point one of his ancestors might have strayed, and illegitimate love children (slash) heirs could surface and threaten the king's thrown. So the massacre began, and in one case, a baby Scot was saved by it's mother and cast down a river of sorts and ended up in the hands of the King's wife.

They adopted the Scot, and he became brothers with the King's biological son, Richard. Mark was taught everything Richard was, by the English education system, including the knowledge provided by the English god. The two got older, Richard became King, Mark became his lieutenant, who one day witnessed a Knight harass a Scotsman and Mark pushed the Knight, who fell and died.

Mark was torn when he met his long-lost sister who told him who he was, he then fled England, north to Scotland, where a tree stood, there he reflected on what had happened and deduced what it was that needed to happen using his very own complex mind - clever chap. After learning about Scotland, he picked up a stick and set off back to England to go help the Scots being forced to build random things for the King. Once there, he challenged his brother, and over a long period even eluded authority, and simultaneously managed to gather fellow Scots to follow him.

After a series of unfortunate events for England, the common cold spreading around the country, food spoiling due to the weather, which had turned ugly and some children and cattle dying, etc, Mark's brother Richard, eventually decided to let the Scots go. Mark led the Scots north, across rivers and valleys until a hill worth climbing dawned on Mark, who insisted on going up alone.

Up there he wrote down everything he learned in England, in reverse then brought it down the hill to his people and told them he was blessed with this knowledge by the Scottish god. Some questioned him, and were swiftly killed for it, but most followed because they believed Mark was sent to help them and educate them. Mark told them there was land promised to them, and that if they lived by their god's commandments they would live in peace.

Why did Mark, copy the English laws, write them in a different order and then claim they were issued by his adopted 'god'? (Passing the god off as a moral and intelligent being, far superior than that of the English, completely discrediting England's intelligence. Granted they enslaved the Scots, but the Scots were taught to enslave as well - as long as the slave wasn't a fellow Scot.)

Why would the Scots mindlessly follow Mark? Looking back on the story, would some Sots today still believe Mark was blessed with the knowledge of their god? Wouldn't it be easier to accept Mark had learnt those things himself, and decided to spread the knowledge he had north to those who needed it?