> but there are several other theories that have more credence with mainstream economists
It's baffling that mainstream economists don't believe this (of course a single event with explanatory power diminishes the utility of the economist profession, and the Upton Sinclair quote comes to mind). In the words of a VERY mainstream economist:
https://krugman.blogs.nytimes.com/2010/02/13/the-case-for-hi...
"when you have very low inflation, getting relative wages right would require that a significant number of workers take wage cuts. So having a somewhat higher inflation rate would lead to lower unemployment"
In short: as a policy, we should reduce the real returns to labor in order to "keep the labor class employed". This policy choice (enabled by the end of bretton-woods) is quite well-captured in all of these graphs. This is how the end of bretton-woods pummeled the lower-income segments of society.
As for how the end of b-w benefits capital owners, inflation makes the cost of long-term borrowing lower, which means that the market price of risk is decreased; and folks with greater means are more effective at capturing arbitrage between the real cost of risk and the price of risk. For example, high finance instruments (like options, shorts, FOREX, etc) have a higher cost to execute in an environment with higher interest rates. If you go to, say, hunter's point/bayview you will not find people taking advantage of these instruments.
Some will claim "the poor are in debt so they will benefit from inflation" but in reality those debts are typically short-term, high interest rate instruments (sometimes even inflation-adjusted as in the case of some low-end home loans), and so the benefit to diminishing the real value of nominal debt is lower for them than it is for the truly wealthy.