According to "continuationists" what explains the 1900 year hiatus? Do "continuationists" (who believe that the signs and wonders of Acts 2 never ceased) explain the apparent 1900 year hiatus as divine sovereignty dispensing early rain then and latter rain now or as 1900 years of a lack of faith and/or understanding?
I'm a Continualist.    Continualism is the just the assumption that the supernatural gifts never disappeared from the Church in the way that Cessionists describe (People who claim that the gifts "died out with the original apostles").    Many traditional Christians like Orthodox and Catholics are defacto unofficial continualists by virtue of their official theology (they believe in saints through history have done various miracles and possessed other supernatural gifts of healing, prophesy etc.).

There are different opinions on the Pentecostal revival:

A) Some see it as being a legitimate work of the Holy Spirit.   (This is some of the reason why the Catholic Charismatic movement took place during the time of Vatican II of the 1960s where Ecumenicism between Protestants was also under way.   Catholics began attending Full Gospel churches and brought Pentecostalism back with them in their Churches.    This made the bishops nervous but was ultimately accepted by the Church hierarchy as something that was beneficial to the Church, but they started their own movement within Catholicism so Catholics would not adopt other Protestant beliefs that were at odds with official dogma and the Magisterium).

B) Others like many Eastern Orthodox will interpret it as being a kind of delusion.   There is a Russian Orthodox term known as Prelest (Spiritual Delusion) that describes when demons grant supernatural gifts to people to feed their pride and so that they may lead themselves and others into heresy and eventual destruction.  That sort of opinion is common among Eastern Orthodox. A monk who convert to Orthodoxy (from Buddhism) named Seraphim Rose wrote a number of anti-Charismatic books and pamphlets.   There however are a number of converts to Orthodoxy who come from Pentecostal and Charismatic churches.  Some of these people have even become clergy, writers and pundits in the Orthodox Church.   Anyway some of these formerly Charismatic Orthodox,believe the movement to be positve, but also flawed or incomplete (Their background set the stage for them to seek Orthodoxy where they claim to have found "The Fullness of the Faith").

C) Personally I believe the Pentecostal revival is something that is both Spiritual (Of God and at times Satan), but also "Socially Constructed".    By Socially Constructed, I mean the assumption that "spiritual gifts disappeared until 1900" is a reality that was originally created by believing in the assumptions of Cessionism (That I believe are historically and Biblically wrong).    So in other words, it was not that the Gifts totally disappeared, but that Protestants have made an interpretation of history in that direction (By ignoring and disregarding the Church History, and hagiographies of Ancient and Medieval times etc.)