Putin was at the top of the revelations, even if the news was unsurprising (but like the Snowden documents, it's not because we all suspected it that the proof is any less valuable).
If the guy who did it is not US authorities, I would not not sleep well if I was him. The police in London regularly picks up the hung or poisoned bodies of those who dared to attack or expose Putin...
http://www.bbc.co.uk/news/business-35998801
Switzerland
Hong Kong
USA
Singapore
The Cayman Islands
Luxembourg
Lebanon
Germany
Bahrain
United Arab Emirates
Panama seems to be down at the low-rent end of the financial secrecy market.
So no - the OP is not only not plausible, but raises more questions than it answers.
Practically, I'd expect a Russian hack to specifically target the tax affairs of Putin's enemies.
This may yet happen now, with Russian and/or Chinese hackers targeting the tax secrets of prominent Western politicians - which would be an interesting development for everyone.
Personally I am a libertarian. I am concerned by the death of privacy and the increasing overreach of governments. I don't really see this drive toward transparency and bullying of countries offering financial secrecy as a good thing.
I have seen or heard of many people who have gone through WW2 and have hidden money in Switzerland. Not to hide money from the taxman. But because they have seen how the governments can easily turn against their citizens and decided they needed a plan B. This concept of "nowhere to hide" is a bit concerning.
Presumably you are talking about Roberto Calvi and Alexander Litvinenko.
While two murders that could be linked to the Russian state are two too many, describing this as 'regularly' seems a bit of a stretch.
That being said, I agree that Putin is near the top of my "people who should not be messed with" list.
There is also Mikhail Lesin in the US.
And these are the ones we know about...
Pretty much that, as well as the fact that Americans are world leaders in tax compliance and these people are three sigma tax dodgers, so there will be disproportionately less Americans among them.
Everyone knows that Russia is corrupt up to the top. How? Pretty much every top politician (and their families) in russia own far more than can be purchased on a state salary. Spokes person for Kremlin is spotted wearing 700,000 Euro watch when his official salary is less than 1/10 of that.
A lot of Russian government officials and their inner circles own multi-million dollar properties in: London, Spain, New York, Boston etc. Their families live in the west, their kids go to schools in usa and europe...
Panama papers disclose how these multi million bribes and shady dealings are accepted and how money is transferred and used to buy up assets overseas. Good old days of a bribe in a suitcase are gone... Its hard to fit $300mil of cash in a suitcase (well Italians would argue lol).
IT IS very suspicious that no high profile Americans were caught in this release... It is possible that USA players simply use different entities to set up shell corps and transfer money using different channels.