Pursuing something like this would perhaps cost more than 200k in the US. And then the startup would likely just fold and you get nothing in return.

Sending a DMCA takedown notice is free.

Unfortunately law being too expensive to pursue makes it practically non-existent. All IP/copyright etc. laws are complete bs because of this.

A large corporation can just roll over you and then say sorry and maybe pay some pocket change money

Hire a lawyer to send a legal notice. Costs practically nothing and since it's an open and shut case, free money for the lawyer (if they charge based on damages), or the startup caves and shuts down.