Given the other typos, this might just be another, but in case it's an error and you might want to use the phrase some other place where it matters:

It's "give it free rein" like a horse you're letting choose its own path and pace, rather than a monarch who would "reign."

You could let a bear reign over all Musk's properties with better results than he's having, but it would be a different sentence.

Both reign and rein can be nouns or verbs:

The Fed is trying to "rein in" inflation.

The "reign" of King Charles the Turd has barely begun.

(Sorry, my inner schoolmarm slipping out.)