The importance of the Magna Carta lives not so much in it’s content as its symbolic significance.
It was the result of having a weak King and strong Barons and did not really impinge upon common people. Yet its power lay in establishing the rule of law and that all people, including the King were subject to it.
This has powerful resonance. For while it was only devised in order to prevent the King exercising his whim to arbitrarily punish whom-so-ever he chose it ended by providing a philosophical premise that all men were equal under the law.
That was a dangerous idea. The idea of equality was out of the bottle and free to impregnate the minds of men with its liberating venom.
Be in no doubt – the ruling classes and wealthy land-owners did not like the idea of ordinary people having any say in how things were run. They still don’t. If common folk felt they were important before long they would start wanting a fair share of the wealth.
The establishment wanted to control what was going on.