It's really not all that sudden. HPE appointed Neri as president back in June. From https://www.sdxcentral.com/articles/news/hpe-appoints-first-... :

The move positions Neri to become HPE’s next CEO, CRN reports.

“This clearly lines up Neri to be the next in line to take the reins of HPE, there is no question about it,” Bob Venero, CEO Future Tech told CRN. “This looks like it is Whitman staying true to her statement that the next CEO of HPE would be born and bred in the HPE family.”