No tenure, no exploratory science and no moonshot. Newton was a dangerous asshole. Would you exchange differential calculus for squeaky-clean academia? I don't think so ...
There's an old quote to the effect that, if forced to choose one thing to destroy: either the Principia Mathematica or the Sistine Chapel*, choose the Principia. The reason? The Principia is a monumental achievement, but it's also universal, and it can be rediscovered. The paintings are the unique creation of one moment in time, unduplicatable.
*Or some other work of art; I can't remember the original exactly.
There's a lot of questions that we need to address, cause and effect in the case of tenure and the general priorities of academia.
First you implicitly assert that tenure effects the cause of emergent moonshots. How much evidence do we have to the contrary? Cursory research shows the modern application in the US dating to the vague "19th century" not a long timeframe. Tenure itself appears to have emerged in the same timeframe. The modern US application of tenure (secondary) was put in place in 1940.
I'll grant you that we have seen a good deal of progress, but I don't know that you could make a robust argument that without tenure, that progress would be absent. I would assert that it falls into inconclusivity, and that to form an argument would require speculation and conjecture. All things are not made equal, and so finding a suitable control group to compare against would be impossible.
We can look at history, though, and see that there was a plenitude of highly driven scientists publishing and advancing understanding prior to the advent of tenure. But to say that we can transpose that to the contemporary model itself is a conjecture.
Simply, we do not know, and can not know.
As to the priorities of academia, and tenured individuals, and the metrics that institutions use to enlighten themselves on the performance of individuals we seem to have come upon a system of perverse incentives. That is exactly everything, to me, it seems we had ought to avoid. Tenured academics can obviously be terminated, but not in frivolous contexts. They are expected to hold some degree of real responsibility. What tenure grants is their freedom of opinion, and the right to fail in their pursuit. As we know, science is the art of failing upwards in a controlled direction.
"In all lines of academic investigation it is of the utmost importance that the investigator should be absolutely free to follow the indications of truth wherever they may lead. Whatever may be the limitations which trammel inquiry elsewhere we believe the great state University of Wisconsin should ever encourage that continual and fearless sifting and winnowing by which alone the truth can be found."
--Theodore Herfurth, 1894
But the cutthroat competition, the model of "publish or perish" elimination, the perverted demand for conclusivity all stand to imperil the actual aims of science. This is all somewhat incentivized by the tenure system, by personal interest, and by the implicit obligation to "realized" progress - except this is of course not real progress. It isn't as concrete as the fundamentals, the traces are laid much finer these days and replication of research appears more often infrequent, while the quality of publications is increasingly called into question and an economy of debauchery contaminates data for capital and personal gain. And thus the bastion of humanity is corroded while evermore maintaining its authority outward. A real hazard if you ask me.
I believe it all needs reform and serious reflection to build it back better.