Do you have a written & signed offer letter? Or is it all verbal/over-the-phone? If it's not in writing & signed, then it's not real.

And as many others are saying, it's a HUGE red flag that the company said they offered the job to more than just you - it's a deal breaker, in my opinion.

Knowing only what you've written here, I would tell the company "thanks but no thanks" and walk away.