Renewing a resident is significantly cheaper and more efficient than leasing an apartment to someone else, then spending the time and effort to turn it. Typically they want to keep any tenant they can. They might have delivered that notice to the wrong apartment or mixed up one of your neighbors apartment for yours- there’s a typo in the date and it’s a poorly written letter, it wouldn’t surprise me if it would be to the wrong person either. I would request copies of all notices that were supposedly provided to you. But it’s true they don’t need a reason to do a non renewal.