First of all, the government won't go down without a fight. Those teaming mobs won't be squaring of with Elon's plucky group of scientists, but with a military tasked with defending them and motivated by a promise of survival for themselves and their families.
Second, we don't have to worry about protecting acres of land-based solar panels from damage if we're beaming microwaves from orbit. The receiving arrays would be smaller, more defensible, and cheaper to maintain. The powersat could be weaponized to defend its own receiving array.
Third, regarding distance, it's really hard to dig more than a few meters underground without heavy equipment.
Fourth, in a total collapse scenario -- no food, air becomes unbreathable due to methane pollution from melting permafrost --, the people remaining on the surface will die off rapidly. The death squads may last longer, but aren't going to be able to present a significant risk to a deep underground military base protected by the members of the former government with a powersat on overwatch.
After the chaos of the collapse, these locations could quickly begin the effort to repair the atmosphere using all of those terraforming approaches that we would not tolerate being deploying today: ocean iron seeding, orbital shades, bioengineering.
Then the hardened survivors could return to a generally functioning planet, and then maybe go to Mars with their newfound skills.
EDIT: This might seem preposterous, but it's far more viable than shipping one million people to Mars and building up a manufacturing base under time pressure capable of keeping everyone alive and fed while also reproducing a supply chain capable of developing integrated circuits on a world with a different gravitational constant.