The reason why you never found an explanation is probably that you never looked for it hard enough, and in any case, your post seems to show that you don't thoroughly understand the issue.
Try reading this:
https://cupola.gettysburg.edu/cgi/v...le.com/&httpsredir=1&article=1188&context=ghj
Schacht, in January 1939, wrote a letter to Hitler, that brought about his dismissal (and replacement with the more pliable Funk). Among other things, Schacht had written (these are only excerpts):
"Especially in the field of daily requirements for the home and clothing, the lack of supply and above all the decline of quality is most evident."
"We are, however, faced with the fact that approximately three billion Reichsmark of such drafts cannot now be paid, though they will be due in 1939."
"Exclusive of the Reichsbank there are approximately six billion Reichsmark 'Mefo' drafts which can be discounted against cash payment at any time at the Reichsbank, which fact represents a continuous danger to the currency."
"We are convinced that the effects on the currency caused by the policy of the last ten months can be mended, and that the danger of inflation again can be eliminated by strict maintenance of a balanced budget."
"We therefore ask for the following measures:
(1) The Reich as well as all the other public offices must not incur expenditure or assume guarantees and obligations that cannot be covered by taxes, or by those funds which can be raised through loans without disturbing the long-term investment market.
(2) In order to carry out these measures effectively, full financial control over all public expenditures must be restored to the Reich Minister of Finance.
(3) The price and wage control must be rendered effective. The existing mismanagement must be eliminated."
(4) The use of the money and investment market must be at the sole discretion of the Reichsbank."
The essay quoted above states:
"While the supply shortage of early 1939 caused the working class to lose confidence in the Nazis’ economic prowess, MeFo bills did the same for businesses and banks. The MeFo bills that jumpstarted Germany’s miraculous recovery also threatened it the most. In March 1938, Schacht ended MeFo financing because he felt the system had gotten out of control.70 Finally Schacht had found a predicament from which
he could not slither out. Many MeFo bills were also reaching maturity and the Reichsbank had to pay back the bills’ worth to their holders. But Hitler wanted to continue financing rearmament to the fullest. Schacht tried to sell long-term bonds to MeFo bills creditors instead of giving them hard cash, but they would not buy.71 His only recourse was to print money and run a deficit. But the rearmament campaign still demanded money as well. To plug this hole, in October 1938, Schacht tried to sell four packages of long-term bonds to the public, each containing 1.5 billion RM. Surprisingly, private savers and insurances funds bought the first three packages but the fourth one suffered a massive failure in late November after Schacht introduced it.72 The financiers of the Nazi economy had lost confidence a couple of months before the workers did at the start of 1939." (bold is mine)
So by early 1939, the so-called perfect storm was approaching. No foreign country wanted to deal in Reichsmarks. Germany tried to do international trade by barter, but they actually had little to export (no consumer goods because they were not producing those; little in the way of armaments because their armed forces wanted those). They managed to strong-arm Romania into a disadvantageous such agreement, but Poland (guess what) said no.
At home, sure the Nazis could unilaterally postpone the payment of the state bonds that came due in 1940 - which they did in OTL, and refuse to pay the MeFo bills - but it is one thing to do that as a wartime measure, and another thing to do that in peacetime. They could use the Gestapo in peacetime too, but they would instantly lose the support of their influential backers, the industrialists and wealthier uppoer classes. They were already losing the support of the workers, who couldn't procure decent food or clothing for their families.
The next step would be the bankruptcy of minor banks and insurance funds, which had invested too much in state bonds and MeFo bills. That would start the panic. Just like the RM was no longer accepted abroad, it would catastrophically lose value at home. Whoever could, say small businesses and shops, would raise prices. Inflation would be rampant.
The government would then enforce stricter price control measures - which, as you should know if you really want to discuss these things, causes the wares to disappear from the shelves and the black market to boom. Even higher prices, higher inflation.
Smaller factories would then go bankrupt, lay the workers off, and stop supplying ancillary parts to larger factories, including those producing armaments.