Why are we having an infant formula shortage?

By design, the US has a massive dairy surplus every year.  Yet we saw in late 2021 a shortage of cream cheese and now we see parents at wits end searching for infant formula.  How can this happen in a country awash in dairy products?  

From the research I have done so far, there seem to be three main drivers:

1) Corporate failure: Abbott Nutrition had to recall three different types of formula manufactured in its Sturgis MI factory in February.  Four babies were hospitalized after consuming formula made in that plant; two of them died.  The plant remains closed until it resolves all the issues raised by recent FDA inspections.  So far a whistleblower at the plant has been fired (who gave the FDA a heads up about food safety issues last October), but I am not aware of any other dismissals.  

2) Market concentration: Two firms, Abbott and Mead Johnson, account for 80% of the baby formula market in the US.  So losing Abbott's throughput for three months is going to be noticed.  

3) Government failure: Baby formula is subject to a 17.5% tariff.  This helps explain why almost all baby formula sold in the US is produced in the US. 

Add panic buying to the situation and, voila, empty shelves and very concerned parents.  Abbott claims it can resume production in two weeks, once they get the go-ahead from the FTC.  It will take another 6 to 8 weeks for new product to get to retail.  In the meanwhile, Abbott and other manufacturers are doing their best to expand capacity.