(The Alto was an experimental development system and did not have a consistent user interface. Many of the innovations at PARC were eventually consolidated by Xerox SDD into the Xerox Star, which provided a consistent interface, metaphor and 'persona' of the computer. The Star was a commercial computer and highly impressive for its time, but not a success. The famous Apple visit comprised a tour of the Alto, but not of the Star. According to their own word, Apple developers like Bill Atkinsons had not seen or experienced the Star. On the other hand, they had read papers from PARC even before the visit and had been influenced by them.)
It may be also worth mentioning that Xerox hired a substantial amount of the talent floating around the ARPANet community. (Bob Taylor, founder of PARC's CS department, had previously headed ARPA IPTO.) Rather few projects emerged genuinely at PARC, many ideas existed already previously and people were hired because of these ideas. (Possible video, "How Xerox Ripped Off the ARPANet Community"? /s)