Scotland had an unparallelled run of minorities from 1406 to 1566. What is interesting is that all Mary's predecessors (James I - James V), with the exception of James III, managed to p;ut aside their regents, reduce the power of the leading noble families and rule reasonably effectively on reaching their majorities, though James I was murdered by his political enemies. Mary's son James VI did the same. Mary did not, though her circumstances on her return to Scotland were really no worse than those of any of the Jameses when they reached adulthood.
She was certainly the wrong person for the job. Antonia Fraser claims that her troubles only started when she married Darnley, but she did, after all, marry Darnley in defiance of all advice and resolved to marry him before she even met him! I think of her as one of those people with a good academic brain, but very little common sense.
Ann