Are they not also one of the causes of that transition?
Now what Walmart did do was to take advantage of the economic detritus left in flyover country as productivity gains and outsourcing started to eviscerate the jobs landscape. But Walmart was not the cause so much as they came along after and capitalized on the ruins.
When I graduated from college and had my first job and apartment, a relatively large amount of my income was spent at the local Walmart. It was a godsend for me at the time. What I didn't spend at all those too inefficient to compete mom and pop stores was money that I could use to pay off student loans, rent, utilities, and still have a little money left over to save up an emergency fund.
Its harder to invest in meaningful job creation when you are spending inordinate amounts of money keeping Walmarts employees fed and housed.
If the Walmart disappears, you don't end up with former Walmart employees with middle class jobs, you end up with former Walmart employees who are now unemployed, require even more government assistance, and have to spend more for staples along with everyone else in town.
Government subsidizing low wage workers is how redistribution of wealth works. That's its mechanism of operation. The rich pay taxes and the government gives the money to lower income people. It would be great if we could just stop having lower income people so we wouldn't need to subsidize them anymore, but where does that money come from? When the answer is higher unemployment and higher prices for other lower income customers, how is it better for the money to come from them instead of wealthier taxpayers?