Sued is not correct.... They were fined by NHTSA . Two totally different things. What we will never know is what penalty they settle for. A $600,000 fine does not mean that is what they will actually pay.
If you are speeding the trooper does not sue you, he gives you a ticket & a fine can result.
Don't know about NHTSA but a large company like Forest River could be fined $7000 (or $70,000 as a willful violation) for a ground pin missing from an extension cord by OSHA that usually being a Serious violation..... So the media could report they had several serious safety violation's and it would sound really bad. I can only assume NHTSA violations could be the same idea.