Of course making an actual bomb is extremely easy especially when you have Pu from the power plants. And Germany has great stealth cruise missiles which potentially can carry those warheads. Yet actually making and possessing a nuclear arsenal is still a pretty large continuous endeavor - all the facilities for producing and storing of the warheads and delivery missiles, the security for that infrastructure, the ongoing technical maintenance of the weapons, all the people of what is, though small, still basically a separate branch of military, maintenance of the readiness level, integration of these weapons into overall military strategy and training exercises, etc.

It is still much cheaper and more effective than a large conventional army, yet sufficiently large and complex to not be doable overnight, so a political situation is required which would allow to, still very quickly, do it.