Because he's insecure and butthurt that Romney called out his atrocious record with new capital ventures:
http://www.npr.org/2016/03/09/469775355/trump-doesnt-own-most-of-the-products-he-pitched-last-night
The NPR goes down the list one by one, but this one might be the best:
Trump Holds Campaign Night Informercial, Lies Boldfaced to Onlookers
http://www.npr.org/2016/03/09/469775355/trump-doesnt-own-most-of-the-products-he-pitched-last-night
The NPR goes down the list one by one, but this one might be the best: