I believe that Russia is doing so well that nobody expected it...
1.- Wars are not quick, there are many factors that are taken into account as the same "Rasputitsa" where the heavy machinery gets stuck in a sea of mud due to thawing.
2.- You have to respect the Geneva Convention, which takes care of the victims of wars, which provides medical rights, human corridors to take out of the cities or towns the civilian people who do not have to be involved in the war and give them humanitarian aid.
3.- To siege a city takes a long time because first you have to let the civilians out of their cities through the humanitarian corridors, once the time to get the civilians out is over, hostilities resume and everyone who remains inside the city is considered as a combatant.
4.- once the site is taken block by block, building by building, which takes a long time depending on the size of the city.
5.- to carry out these operations requires that the Russian army has a 10 to 1 offensive to be able to do it, that involves a lot of resources and time.
The economic sanctions applied are affecting not only Russia but the whole world, now Russia being the number 1 country in oil and gas production is the least affected in this regard, since 40% of the gas consumed in Europe comes from Russia and as an example Germany depends between 60 and 80% of that gas and oil, so it is not at all unwise to bet that the German economy would be the first to fall and then successively the other nations.
On the other hand, Russia cancelled the North Stream 2 and now does business with China to export 50% of the gas that China needs, it is as if it was useless to take that business away from Russia.
The same goes for fertilizers, since Russia is also the number one country in fertilizer exports, which leads us to expect a rise in food prices.
With this said, it is important for a country to be self-sufficient in every aspect and not to depend on other countries for essential things (energy, oil, gas, food).
And here I could spend more time explaining why a war is not easy and fast, unless you get into a country that has no way to defend itself and even then they would find resistance for several years.
With this said, not because of what I am saying does it mean that I am in favor or against one or the other, war is ugly on any side we see it and the end of them is when the people rise up against their governments and stop all internal economic activity so that the governments and those who finance such things know that they are not the ones in charge of the world.