It's not easy to dig up info on the 2012 coup d'etat of Mali. But some nice pearls can be found out there.
https://www.nytimes.com/2012/03/23/world/africa/mali-coup-france-calls-for-elections.html
From this article we can learn that the 2012 coup was done by low ranking officers and even enlisted soldiers. The leader was a captain (Amadou Sanogo), and their spokesman was a lieutenant. Now we can read about colonels related to this year's coup.
The army of Mali back then, was 7000 strong, this was reinforced through the years since then. Still considering it's pretty weak and have to cover a large country.
But more importantly the article says that the Tuareg rebellion - which led to the destabilization of the country and triggered the coup - was made possible by the arms the Tuareg fighters obtained in Libya's revolution which deposed and killed Gaddafi, and brought back home.
They link this article, which contains more info about this:
https://www.nytimes.com/2012/02/06/world/africa/tuaregs-use-qaddafis-arms-for-rebellion-in-mali.html
The Tuaregs gained considerable firepower. Beside their trusty Kalashnikovs now they could deploy machine guns, mortars, anti-tank and anti-aircraft weaponry. They also had first hand battle experience, and started the rebellion with about a thousand soldiers. It seems religious fanaticism also made them more dangerous. Mali's army proved to be impotent against them.
Gaddafi's role however is more deeper than this. Apparently his country played as a base camp, training center for Africa's rebellious groups for decades now. He also supported separatist and rebel movements all over the continent. Tuaregs themselves got their drills while visiting their Libyan cousins basically. In Mali Gaddafi also was a foreign benefactor who helped to develop the country, but the Arab Spring and his death resulted in a conflict still haven't resolved.
The article closes with a quote from a Malian lawmaker:
“The Westerners didn’t want Qaddafi, and they got rid of him, and they created problems for all of us,” he said. “When you chased Qaddafi out in that barbaric fashion, you created 10 more Qaddafis. The whole Saharo-Sahelian region has become unlivable.”

I also found an interesting website:
https://www.strategypage.com
They published a few articles about Mali, I'm gonna check those sometimes. The site main profile is military news, so I'm hopeful.