I would argue that neoliberalism is a symptom and a cause.
Economic models have a moral aspect and are not the neutral eternal truths they claim to be.
As you point out the era prior to neoliberalism was shaped by the experiences of WW2 and the Great Depression where people saw the result of deregulated markets and conflict between rival powers.
Both shaped the pre neoliberal era in significant ways.
WW2 left behind a belief it was important to avoid hatred between groups and that tolerance should be prioritised. This resulted in the increased 'diversity' that is now almost universal in western democracies. 'The Return of Great Gods' explores the reaction to this that is part of what is unfolding now in phenomenon like Trump in the US and far right groups in Europe.
The Great Depression certain left behind an emphasis that 'free enterprise' has limits and that unregulated markets tend to be volatile and go through boom bust cycles which can cause huge societal and economic dislocation.
The mixed economy such as that which developed in NZ from the 1930s until neoliberalism arrived in the 1980s saw collective ownership of strategic infrastructure which was seen as important to the wider economy to be trusted with private ownership. Banking was partially collectively owned with co-operative savings banks, building societies and government owned banks allowed to issue housing mortgages but commercial banks required to only finance commercial enterprises.
All of this required a degree of collective management of major economic activities from banking, electricity generation and distribution, insurance (nearly all insurers were mutual) to the railways and telecommunications.
What faded was the will to manage these strategic assets in a collective manner, for the common good.
What rose was banks and financial consultants and lobbyists who argued strongly that they could manage these assets better. They were the neoliberals.
Did they rise because by the 1970s the sense of collective will and unity that had emerged from the Great Depression and WW2 had faded? I suspect this was a major factor at least.
We see this now in USA- a now highly diverse society- one that led the charge into neoliberalism, one that for a long time enjoyed considerable profits from the acquistion and sale ot ongoing control of many strategic assets globally via the neoliberal agenda.
For example NZs community savings banks were sold off to the US shareholder majority controlled Aussie commercial banks like ANZ and Westpac which today control over 80% of NZs banking and mortgage issuance.
Banks came to enjoy huge influence over politics.
Bankers came to be prime ministers in NZ, Australia, Canada and all across the liberal western democracies bankers came to enjoy political power through both sponsorship of politics and actual infiltration of politics.
The same for insurance.
NZs largest mutual insurer which dominated NZs home insurance much to the chagrin of foreign insurers like IAG was eventually sold to IAG by the John Key (ex BoA, banker) PM government in a forced sale which as caused by neoliberal undermining of NZs natural disaster scheme.
Neoliberal politicians backed by banks and corporate sponsors gradually dismantled the mutually owned mechanisms which had formed the backbone of the mixed economy.
In some cases it can be argued improvements in efficiency have been made, but in many the opposite is the case- instead privately owned strategically important parts of the economy act solely out of self interest to extract the maximum profits possible with zero regard for the effect on the wider economy- because it is not their job to care about the wider economy.
At the same time China has risen where there is still a very strong sense of community and the economy is very much run along the lines of seeking to obtain the maximum possible results as a collective- as China can. Private enterprise is allowed where it cannot monopolise or capture rentseeking advantage but major strategic components are developed with the whole of the economy foremost in mind.
Electricity generation and more broadly energy development strategy is developed with Chinas economic competitiveness in mind.
The result has been China produced electricity for its citizens and businesses at less than half the cost of any competing major manufacturing economy.
By producing electricity in a collective model and providing it to competitive businesses at the lowest possible cost, China Inc gains a significant advantage over all other manufacturing nations.
This model is repeated over and across all strategically important areas of the economy- the result has been Chinas mixed economy now dominates global trade in manufactured goods and commodities.
USA is now responding in militarily to maintain its petrodollar hegemony by cutting off Chinas energy supplies and trading partners.
Ultimately who triumphs might hinge of how united in sense of purpose each is.
Neoliberalism has seriously eroded the sense of national unity in every nation it has operated.
Whether this is a symptom or a cause- or more likely a bit of both, can be argued.
But unity of purpose is something China has carefully maintained and cultivated.
It is perhaps something that strengthens under shared hardship but withers with wealth and global dominance.