I remember reading the Foundation Trilogy long ago. I liked it -- it has a grandiose sweep of history. One could watch the Foundation grow from being a tiny colony of exiles from the Galactic Empire to the ruler of a new empire that spanned 1/3 or 1/2 of the Galaxy when the trilogy ended. Something like watching the United States grow from a few small British colonies to the a nation much larger and powerful than its parent. One could also watch the Galactic Empire fall apart, starting at its outer edges and going inward, in a fashion inspired by historian Edward Gibbon's Decline and Fall of the Roman Empire.
My favorite part of it is in "The Mayors", where the Foundation creates a religion of its advanced technology to rule some neighboring planets. The leader of one of these planets, Prince Regent Wienis, decides that he wants to conquer the Foundation. Conveniently for him, the Foundation's technician-priests help refurbish an old Imperial warship. But they install on that ship a super holy device, an ultrawave relay. When Wienis orders the invasion of the Foundation's world Terminus, that ship, renamed after him, is the first to go on its way. Then a Foundation technician-priest curses the ship for going on a sacrilegious expedition, and we find that that device is a kill switch.
The Mule is a joker in the deck that Isaac Asimov's magazine editor John Campbell insisted on putting in. While IA was content with surmounting Seldon Crisis after Seldon Crisis after Seldon Crisis, JC decided that that would eventually get very dull and demanded something that would disrupt that orderly succession. So IA thought up the Mule, and in the trilogy, it took a lot of effort to recover from his disruptions and get the Seldon Plan back on track.
As to the Encyclopedia Galactica being like Wikipedia, how would it be different from any other encyclopedia in that respect?