DJS,
I appreciate your response. You are more optimistic than I am.
Since we are talking hypothetical situations the predictions are going to be based on our individual premises and not on some kind of certainty.
Any event that involves multiple causes has a 50% chance of happening.
If a person were to say that they are 60% sure an event will take place it would mean that you have access to information beyond simply guessing.
If you say that you are 70% sure an event isn't going to occur you would have some knowledge beyond just stating the possibility.
I acknowledged the fingerprint issue when I mentioned isotopes. That would only be an issue if you could map the route taken to get the device to its point of detonation. Russia would be able to deny its involvement unless someone blew a whistle on the conspiracy and evidence could be established beyond resonable doubt that Russian authorities were behind such an attack.
Oligarchs are not the likely source of such intrigue. That was only thrown into the mix to consider multiple possibilities.
Suitcase nuke is really an expression that did have some credibility at one time. It is not impossible for Russians to rig a device that could blow up lower manhattan and be small enough to escape detection. The device could be moved into place from multiple sources and assembled without detection. The most difficult thing would be delivering the fissile material that would be easy to detect. However, it's not impossible when you consider the creative ways to cross international boundaries in a country that has thousands of mile of unattended coastlines. If Tom Clancy were alive he would have a list long enough to write a library of spy novels. There might even be some devices that are already in place from the 40 year long cold war with diplomats coming and going with various degrees of immunity.
Putin isn't motivated by money - he's not a businessman. He is motivated by power and control. He could have disappeared with his billions a long time ago. Putin wants to throw off the influence of the United States. He wants to change history. Putin cares about Europe because they are his neighbors and he respects their culture. Putin detests the monopolar world controlled by the USA. Biden is talking about the US and Great Britain doing maneuvers with Ukrainian troops. This creates a situation that would be very tempting for a man like Putin to carry out the kind of terror I mentioned.
So is this likely? I can't say. You can't say. Not having extraordinary knowledge it's a coin flip. Things don't happen until they happen. Evoltuion tells us that given time anything can happen. Who would have bet that terrorists would hijack four Jet Airplanes and synchronize an attack on two landmark NYC buildings and the Pentagon and a fourth unknown target. On a warm fall Monday we all went to sleep as we heard the usual planes flying over our dwellings. Tuesday morning we woke up to a smoldering New York skyline. Remember you are dealing with a man who came to power with the backdrop of destruction of hundreds of poor people killed by solid rocket fuel bombs in their apartments at night.