TL;DR is that companies were putting cheap filler aminos like taurine and glycine into protein powders, which would pass as nitrogen on a "protein" test, but they were far cheaper and less effective than actual whey protein.
A lot of times the companies would think they were getting legit raw materials, but if they didn't test their incoming raws (illegal per cGMP), they could easily get screwed by the cheap crap coming in from China.
It's expensive to test for ($2000 for a full amino panel), but once the bad guys started getting discovered, the class action lawsuits hit hard. One multi-million dollar settlement's already been public.
Olive oil companies are wise not to get caught doing this, especially the bigger ones with deep pockets (a class-action lawyer's dream). Always test your incoming and outgoing product. If you blindly trust that overseas manufacturer's lab tests, get ready to get destroyed.
[1] https://blog.priceplow.com/protein-scam-amino-acid-spiking