It was no retreat, it was a rout. Russian soldiers dropped their toys and equipment, and instead took home as much loot as they could. No wonder they couldn't take their own dead soldiers home with them. This isn't a well drilled army, its just a bunch of thugs who purposefully mass killed citizens.
After this, their morale will be at an all time low. Even if they are convinced to move to the east, they will be in no shape to make any large difference.
I've been to Ukraine a couple of times - in the cities, they have a good standard of life; not that far away from a moderate western economy. Been to a couple of small towns as well - buses are decades old, not so many modern cars, but, even there, the standard of living is ok.
Haven't been to Russia, but have Russian friends and people who've lived there. Apparently central Moscow is insanely wealthy, but by the time you move into the suburbs, it's ****ed - and the villages are dirt poor with barely basic infrastructure.
This matches up with the behaviour of these soldiers - and their calls to home where they express disbelief at how "rich" the Ukranians are.