I've heard stupid before. But this pretty-much takes the cake.
Describing Mars as "a fixer upper of a planet," Musk noted that the main problem with our red neighbor is that it's too cold for inhabitation. But, he noted, it can be made to more closely resemble Earth if we just warm it up. "There's the fast way and the slow way," Musk said, with the slow way being the gradual release of greenhouse gasses, which are famous on Earth for causing global warming and climate change.
There's dumb and then there's really dumb. This falls into the second category.
Mars lacks an atmosphere of material density because it was stripped off by the solar wind.
The reason it was stripped off is because Mars lacks a molten iron-bearing core in the center of the planet, which Earth incidentally has. This is why our atmosphere wasn't stripped off -- it is protected from having that happen by the magnetosphere, which is a magnetic field generated by the spin of the earth and that molten iron-bearing core.
Nuking the planet would eject warm material above the surface (of course) and it would circulate as an "atmosphere" for a while (albeit likely high in various radiological elements) but it would be stripped off by the solar wind just the same.
This is a huge problem for water-vapor molecules without which an "atmosphere" has no material value in terms of sustaining life. Venus, for example, has a dense atmosphere but almost no water in it because it too lacks a magnetosphere.
There are people who have talked about attempting to trigger a "runaway" warming effect by finding the means to sublime the CO2 (existing as dry ice today) at the Martian poles. This is an interesting idea but doesn't solve the problem in any material way, in that you still wind up with no water vapor of note in the atmosphere and any that does manage to get in there is subject to being stripped off. Since the supply of such material is finite releasing more of it is only a "temporary" victory, comes at extreme cost, and doesn't reach the goal.
But then again neither are lithium-battery electric cars.....
