The lesson take-a-way here is that brokers should check their carrier partners often for compliance.
Convoy could not have known about the driver - no broker can ever manage that. It may be that this carrier was in compliance when first signed up. Convoy's negligence here is that they negotiated a new load (or contract extension it should be called) to someone who should have never gotten the work.
If the plaintiff can prove that Convoy never checked this carrier and prove they utilized numerous entities that are in the same situation they have a solid argument. If Convoy's policy is to check monthly or for each load and it slipped past, then they're in trouble especially since Convoy's business model is very technically focused and should be able to glean this information almost instantaneously and stop it in its track.
I'm surprised that the plaintiff did not name the FMCSA. Something has to be done on the lack of enforcement.