Mearsheimer gave a whole lecture on this subject back in 2016 that I highly recommend watching. Mearsheimer is certainly not pro Russian in any sense, and he comes from the realist school of US politics. First, here's the demographic breakdown of Ukraine:

here's how the election in 2004 went:

this is the 2010 election:

As we can clearly see from the voting patterns in both elections, the country is divided exactly across the current line of conflict. Furthermore, a survey conducted in 2015 further shows that there is a sharp division between people of eastern and western Ukraine on which economic bloc they would rather belong to:

After a violent nationalist coup overthrew the government back in 2014, the eastern parts of Ukraine declared independence. Ukraine has been in a civil war since that time. There were attempts to resolve this with Minsk agreements, which the regime in Ukraine and its western backers ignored. We've now had admissions from prominent western politicians that the goal of the agreements wasn't to implement them faithfully, but to buy time.

Furthermore, lots of prominent western scholars, like Chomsky, have explained in detail why Russia ended up going to war:

• https://truthout.org/articles/us-approach-to-ukraine-and-russia-has-left-the-domain-of-rational-discourse/
• https://truthout.org/articles/noam-chomsky-us-military-escalation-against-russia-would-have-no-victors/

Even Stoltenberg admitted that the war was ultimately a result of NATO expansion, and could have been avoided:

He wanted us to remove our military infrastructure in all Allies that have joined NATO since 1997, meaning half of NATO, all the Central and Eastern Europe, we should remove NATO from that part of our Alliance, introducing some kind of B, or second class membership. We rejected that. So he went to war to prevent NATO, more NATO, close to his borders. He has got the exact opposite.

https://www.nato.int/cps/en/natohq/opinions_218172.htm

50 prominent foreign policy experts (former senators, military officers, diplomats, etc.) sent an open letter to Clinton outlining their opposition to NATO expansion back in 1997:

George Kennan, arguably America's greatest ever foreign policy strategist, the architect of the U.S. cold war strategy warned that NATO expansion was a "tragic mistake" that ought to ultimately provoke a "bad reaction from Russia" back in 1998.

Jack F. Matlock Jr., US Ambassador to the Soviet Union from 1987-1991, warning in 1997 that NATO expansion was "the most profound strategic blunder, [encouraging] a chain of events that could produce the most serious security threat [...] since the Soviet Union collapsed"

Even Gorbachev warned about this. All these experts were marginalized, silenced, and ignored. Yet, now the history is being rewritten in the west to pretend that Russia attacked Ukraine out of the blue and completely unprovoked. The reality is that Ukraine is simply a western proxy in a war between Russia and NATO.