Neither of them started the armed resistance against it, either, though Mandela obviously participated in that.
Note that net-net, the invention of dynamite probably saved many lives. Nitroglycerin-based dynamite invented by Nobel isn't very useful for military purposes, and has never been in wide military use. It can't be safely stored for long periods or in hot conditions, making it ill-suited for battlefield logistics. Nitroglycerin-based dynamite is primarily used in mining and earth-moving.
Properly stored, dynamite is both much safer and more powerful than the black powder or liquid nitroglycerine that were primarily used in mining and earth-moving before the invention of dynamite.
Much later, "military dynamite", a more stable dynamite substitute devoid of nitroglycerine and more suited to military use was developed. While more stable, it's more expensive, and less commonly used. I don't believe Nobel had anything to do with the development of military dynamite.
And then he proceeded to bomb the fuck out of Iraq, Syria, etc.
It was disappointing, but unsurprising that 2009-20?? has gone down more or less the same road.
To name one: Hume & Trimble (1998) was considered ironic because it was viewed as kind of reward for ceasing violence they initially caused. Similar remarks were made in 1993 about Mandela and De Klerk. It can even be argued that Gorbachev and Carter had blood on their hands before becoming saints.
Maybe this kind of ambiguity is simply rooted in the fact that the monetary price is paid by the deeply ironic invention of dynamite by Alfred Nobel.
' Guess "contribution to peace" is less about ethics and more of a political concept.