Let's just say that hindsight is 20/20. The EU got the prize in 2012, before Russia annexed Crimea.
Preventing wars through commerce and economic relations more generally isn't a 100% guarantee, just statistically more likely according to a number of studies. (There are number of counter-factors [discussed in there], including disparity in perceived military power etc., which definitely played a role in Russia-Ukraine as they did in other conflicts.)
Anyhow, you could say the Comecon plan failed much more miserably, in the end, with Russian and Ukraine fighting each other.
And it's a well known fact that Germany and France did less to help Ukraine militarily before 2022 than the USA did. So that was the EU peace plan for the region. (Appeasement, one could say--and in fact some did phrase it just like that, at least in the aftermath. Finally one might say that the intensification of Russian autarky plans after 2014 did bear some resemblance to the Nazi ones, so the EU failed to heed that lesson, in hindsight. And going back over a decade or so, the "half way" policies of EU back then towards Ukraine were also considered appeasement of Russia, by some. Although evidently they were ultimately not appeasing enough for Putin. Who knows how accurate this recollection is, but according to one Georgian ambassador to the EU, some EU officials were sure Putin would not do what he did in Crimea, before 2013, that is.)
FWTW, I think almost everyone forgot about this by now, but around 2010 the EU had a more rosy vision for the relevance of economic relations with Russia, in the "Partnership for Modernization":
Concluded in 1997, the EU-Russia Partnership and Cooperation Agreement (PCA) still constitutes the legal framework of the EU-Russia political and economic relations (European Communities 1997). It contains provisions on trade in goods and trade in services based on the GATT most-favoured nation treatment provisions and GATS, respectively, but does not link trade to either a peace or security agenda. In line with Art. 1 and Art.3 PCA, the Parties considered negotiating a new agreement, but these attempts failed amid Russia’s use of force in Georgia and energy security issues, i.e. Russia’s weaponization of gas supplies to Ukraine and Moldova (Dettke 2011).
In 2010, the EU and Russia announced a Partnership for Modernization as a framework for ‘promoting reform, enhancing growth and raising competitiveness’ (Council of the European Union, 2010). As the initiative was advocated by Germany, it is characterized in the literature as the ‘Ostpolitik for Europe’ (Stelzenmüller 2009). It was adopted as a response to Russia’s newly elected President Medvedev’s suggestion to create a new security architecture in Europe, involving both NATO and the former Warsaw Pact institutions (e.g. the Commonwealth of Independent States, CIS) (Dettke 2011). Interestingly, ensuring the openness of Russia’s economy through its WTO membership lay at the heart of the EU’s vision for Russia’s modernization. Thereby the Union hoped to develop a network of new trade agreements which would foster a large free trade area including the EU, Russia and Eastern Neighbours. Thus, from the EU perspective, the Partnership for Modernization with Russia should have become a new valuable dimension of its efforts to promote prosperity and stability through trade on its Eastern borders. Moreover, the EU’s hopes to link Russia and Eastern Partners within a large free trade area in the aftermath of the Russo-Georgian war clearly followed the liberal peace logic or, put differently, sought to use trade to prevent another war in the Neighbourhood. There is no single reason why the Partnership for Modernization did not become a reality. The most evident one is that the window of opportunity for EU-Russia ‘constructive bilateralism’ closed after the 2012 presidential elections in Russia and Putin’s return to power (Fix 2021). Besides, the parties had different ideas about what modernization should mean, with Russia refusing to include political and institutional matters into the modernization agenda (Dettke 2011). The Partnership de facto ceased to exist following Russia’s 2014 annexation of Crimea [...]
It's clear that the EU could not leverage economic ties with Russia in exchange for certain (internal) reforms [that may have translated into foreign policy ones] as it could with smaller neighboring countries.
I almost forgot about this too. But after 2008 (their intervention in Georgia), Russia also saw the EaP (EU's partnership with some countries in the former Soviet space) as nearly the same thing as NATO:
A noteworthy development in this regard was Russia's vehement reaction to the launch of the EaP in 2009. Moscow condemned this new EU initiative in terms that had until then been reserved for NATO. Although it was confined to the level of rhetoric, such animadversion appears quite puzzling since, as was emphasized, the EaP is a rather modest bureaucratic initiative that mainly regionalizes instruments that already existed in the ENP framework.
The term then used by Lavrov in the EU's EaP was "sphere of influence" and he later argued that such an expansion of EU's relations would ‘push Russia out’. The accusation would then be repeated over the years, in nearly identical terms. (The strong Russian reaction may seem a bit puzzling, but according to some Western analysts the fact that none of the EaP countries endorsed Russia's recognition of Abkhazia and South Ossetia [as independent countries] may have had some kind of electrifying effect in Moscow.)
Although the West paid a lot more attention to the (2010-2011) announcements of the Eurasian Customs Union (ECU) and the Eurasian Economic Union (EEU), as pointed out in Putin's article introducing the latter, the effort had been in place since 2000 as the Eurasian Economic Community. So one could say that Putin's Russia always intended to be the center of a single market of its own, in sync with the Russian foreign policy motto that the world needs to be "multipolar". (Whether that was intended or not, economically speaking, Russia accounts for about 90% of the EEU's GDP.)