If you're so smart, how come you're not Machiavelli?

We live in a world where the adjective 'Machiavellian' connotes material success gained by unscrupulous means. How is it, then, that Machiavelli spent time in jail? I don't know the answer to this, and it's a question that's been plaguing me for years. So I thought I'd muse aloud, here.

If you haven't read Machiavelli's The Prince, I strongly recommend you do. It's Free. Ok, back now? Good book, isn't it.

Machiavelli wrote that book in the tradition of Mirrors for Princes, seeking to influence the Medici rulers of Florence. My learned mother-in-law says The Prince is an example of a style of literature called 'de Regimine', but whether this means 'on Ruling' or is a shortened form of 'de Regimine Principum' and means 'on Ruling Kings' I cannot say.

What is clear is that (through his writing) Machiavelli sought influence over his Prince through reason, which could be considered a pretty noble aim (or if you're an unreconstructed Nietzschean, a ruse by which Sklaavenmorale sought to undermine then overpower its more noble oppressor.)

I'm assuming that Machiavelli wanted to govern by proxy, by dint of reason, through articulation of principles, under the precept that the pen is mightier than the sword ... and given that he's pretty confident and unequivocal in his assertions in the book ... how come he was first suspended from a ceiling like some kind of highly literate chandelier?

Why did Machiavelli find himself being tortured in prison?

Sun Tzu says the greatest general is not he who fights the most battles, but one who wins every battle he fights. So why did Machiavelli lose the battle when the Medicis came to power, and find himself subjected to the medieval version of waterboarding?

Is it rather that something was revealed to him as he hung from the rope by his wrists? Some kind of epiphany-in-mortification? They showed him the instruments of torture and he suddenly realised he needed a whole new career?

I don't know Machiavelli the man, can't know his innermost thoughts, but still I want to understand his mistake, so I'm going to present some cases:

Was his book an attempt to re-narrate his own part in history, sublimating his rage and explaining to himself and his new boss why he'd been cast down from his walk-on part as military diplomat. Was he sharpening himself as a willing tool, to be bent to whatever purposes his Prince desired. Was it an apologia for the cruelty of the Prince? Was it a Resume, a desideratum, a memoir?

Or was his imprisonment due to a last ditch personal resistance to the new Medici rule, akin to Thoreau's

if one HONEST man, in this State of Massachusetts, ceasing to hold slaves, were actually to withdraw from this copartnership, and be locked up in the county jail therefor, it would be the abolition of slavery in America.

Or was The Prince a big old 'Told you So!' to the people to whom he'd been loyal? Perhaps he'd given the previous regime advice that'd been ignored, and he now wanted to get it down on paper.

Or was Machiavelli just not quite as clever as he thought he was?

Or was it just a new broom sweeping clean? The Medici came to power, Machiavelli was on the wrong side and was tortured as a matter of course?

Or are we entitled to summarize Machiavelli's mistake as "It's all about the capricious exercise of power, Stupid!"