4 ideas
At the Congress of Vienna in 1814–15, Talleyrand represented defeated France yet won a seat among the four victorious powers. He did it by casting himself as the defender of 'legitimacy' and the rights of the smaller states, then exploiting the quarrel over Saxony and Poland. In January 1815 he signed a secret alliance with Austria and Britain against Russia and Prussia, turning France from the defeated party into the arbiter of the coalition.
On this view betrayal is a matter of timing: moving before the fall reads as foresight, moving after it reads as treachery. What stays constant is the interest being served, while its occupants change.
Talleyrand's quip that treason is a question of dates recasts betrayal as a judgment about when to act. He then presided over the provisional government that deposed Napoleon in 1814.
Talleyrand survived by making himself too useful and too well-connected to discard. He held relationships across every faction, émigrés, revolutionaries, bankers and foreign courts, so each new regime needed him as its bridge to the others. He paired this with deliberate slowness, 'above all, not too much zeal', which kept him from committing early to losing positions and left every option open.