She had to go. Multiple factors.
On Fiona Hyslop's watch, teacher numbers had dropped substantially: a development she herself described as "unacceptable" - although that epithet was aimed at local authorities, whom she blamed.
It was becoming difficult for Alex Salmond to defend her in the face of such statistics. In such circumstances, the first minister has to bolster his own reputation - and sacrifice that of a colleague.
Another factor is the Scottish government has now embarked upon a review of educational provision which will explicitly question whether local authorities are the right delivery vehicle.
Ms Hyslop announced the review on Friday, buried within a substantial attack upon councils for their record in spending resources supposedly provided for teaching.
But Alex Salmond believes that thinking is needed to pursue that review. Hence, well-merited promotion to cabinet for Mike Russell.
And one more motivation. The Liberal Democrats were about to pursue a motion of no confidence in Ms Hyslop.
They were planning to take that to Holyrood's business bureau this afternoon, with a debate scheduled for Thursday.
Government aides insist that wasn't the prime factor in this demotion for Ms Hyslop.
They say Alex Salmond was considering refreshing his team anyway in the light of the disappointing teacher stats.
However, at the very least, it will have concentrated minds.
On previous occasions, when opposition parties have talked of confidence motions, Mr Salmond has let it be known that an attack on one of his team would be interpreted as an attack on the whole government.
This time, he decided against such an approach. He has concluded Ms Hyslop should be moved, rather than defended at all costs.
She is consequently demoted - and faces a cut in salary.
However, it is a notably soft landing. She remains a minister, taking Mr Russell's portfolios of culture and external affairs.
She will continue to attend cabinet regularly - although no longer a full member.
That reflects three elements: Mr Salmond's admiration for her talents; his belief that she did a good job in elements of her previous brief, such as further and higher education; and his understandable reluctance to concede complete victory to those opposition critics who were demanding her sacking.
This is, self-evidently, bad news for the Scottish government. It speaks of vulnerability and poor performance in an area which is important to many voters.
Looking ahead, three challenges.
Can Team Salmond restabilise after this: a demotion enforced by ministerial failure?
What happens to that review of education provision? Councils will complain, fearing a loss of their power.
But, starting from first principles, are they the best to deliver education?
Could that be done by central government? Or trusts? Or by giving more power to individual head teachers, under central supervision?
Local authorities should not presume that Scots will automatically endorse their role.
They will have to defend it, explain it, justify it and, above all, prove that they are spending limited resources in the most efficient manner.
In truth, that may be the outcome: that councils feel obliged to review and upgrade their own performance in the light of an explicit threat from central government, albeit one that may be elegantly expressed by the new cabinet secretary.
And, thirdly, what happens to Mr Russell's constitution brief, now assumed personally by the first minister?
I think change derives partly from necessity. Mike Russell will have enough on his hands with education.
However, it also reflects where we are on the constitutional issue.
Mr Russell has published the white paper.
It appears the referendum will not happen next year.
The next stage, then, is political, rather than governmental. It is about strategic positioning to advance the SNP cause of independence.
One for the FM.