"We get sued all the time, so how could we have known this was a special case?"
They seem to have significant problems. Its broader then "not discovering" 5 minus 1 million of documents. There seems to be multiple smoking guns in evidence: https://www.justice.gov/d9/2023-09/416652.pdf Google internal Email instruct: never to talk about 'market share' or even 'markets'. This is clear and deliberate behaviour to evade government regulators. It is institutionalised through legal training class 101.
Disclaimer: not a lawyer, CS professor with some courtroom experience.
That seems like a no-brainer thing a company should be doing.