Sachs is a liberal economist who rose to fame with high profile anti-poverty NGOs, WHO and the UN in the early 2000s. The anti-poverty programs he worked on in Africa and other third world nations moved around a lot of money and had Sachs hobnobbing with celebs like Bono and Matt Damon. But their efficacy was questionable.
I think Sachs fell in love with the spot light and turned to political punditry to keep himself in the media. He has been more comfortable in progressive circles and worked with Mark Weisbrot at CPRC on the impact of Venezuelan sanctions. But he has also drifted into more of a horseshoe range with dark web right wingers with odd positions on the Uyghur genocide in China and then most recently adopting his very flawed analysis of the war in Ukraine based on an amalgam of progressive and right wing anti-western imperialism riffs.
His theory is basically that the West sought to destroy Russia in the post-soviet era through NATO expansion and unfair monetary integration procedures that badly tanked Russia's economy after the fall of the USSR.
The "not one inch further" to the west quote is a very dishonest argument. First, it was never memorialized into a treaty. Gorbachev was a career politico and his diplomatic team were some of the most experienced negotiators on the planet. They knew full well that anything said off the record wasn't worth diddly squat. The Soviets could have negotiated to include a deal to prohibit NATO expansion westward in part of the deal to reunify Germany but didn't do so because the Soviet satellites were draining Russia of resources. The USSR needed to dump expensive satellites like E. Germany to try to buy itself some time before the economy collapsed and people stormed the Duma in revolt.
Also, Sachs never talks about Russia's 1992 agreement with Ukraine in which Ukraine gave up its nukes in exchange for territorial guarantees. And Sachs never talks about Russia's post-Soviet aggression in Georgia, Chechnya, etc. that had the former satellite states shaking in their boots and begging to join NATO.