Jane Grey was a really a tragedy, as she was very intelligent, and had so much potential, but then she was executed so young, and she didn't even do anything execpt what she was manipulated to do. Her parents were and others were really those who were guilty. Very sad, although it might have had it's good points as well.
So many people then died young, but she was killed young, and with that lots of promise was lost, just as much as if she had died young from natural causes, which was all too common. Her parents were very bad to her to her, they just wanted power, and rather than get it overtly, she would be the figurehead, and they would have the power!
This was unfair, and she got executed for what they did, they more likely ought to have paid, if anyone was to pay. But Jane was a symbol, one that could not be allowed to live of insurrection against Mary, and Mary knew this. So Jane was killed as a symbol, rather than as a person, something all too common in that age. Technically, she was a traitor, and she had been Queen, even if this was not what she wanted, but rather her parents. So her execution is understandable given this, for Mary I was a kind woman, but one who knew you had to watch your back carefully, and make sure there were no enemies. If Mary was in power one day, it could so easily have been Jane Grey the next, and Mary being executed, so she was compelled to end the life of her innocent cousin. Jane was very protestant, and I agree this was more personal than political. But in that age, sometimes if a ruler had complete control over things, the two became the same. So perhaps Jane would have been led to serious religious intolerance in later years, but it is impossible to say.