Because he doesn’t have to, obviously.
Why should Trump spend his money to resolve Cruz’s problem?
Furthermore, the longer Cruz leaves it out there, the longer it could work against him.
“...Furthermore, the longer Cruz leaves it out there...”
I don’t believe Cruz has any standing to engage a court of competent jurisdiction.
He can’t sue himself...
He can’t pop down to the “Presidential Qualification Dept” and get a “running for president license”...
He can’t ask/beg/force any court to pre-review an imaginary lawsuit that some other candidate may or may not bring...
However, I do believe Trump has standing as a competing candidate. So if Trump is serious about it, he can do something. Will he be all talk and no action? It remains to be seen. In the meantime, it just makes him look like he’s flailing desperately at a rising competitor, grasping at straws, unable to compete on the laundry list of “yuuuge” issues the nation faces.