Charles J. Brown, in his book, The Ministry: Addresses to Ministerial Students (and Iain Murray in the biographical introduction) answers that question.
There is one particular hindrance to such a revival and Charles Brown often spoke of it. He noted how, in periods when spiritual conditions are low, love and forbearance grown weak while disputes and controversies among Christians become common.
When, in his words, ‘There is little communion with God, little striving against sin, little pressing after the divine image,’ then, ‘Disputes and discords rush in to fill up the very vacuum.’ He continued:
I am quite well aware that, in existing circumstances, many controversies must be continued; but let the church only be revived � let a spirit of faith and holiness be but poured forth � and the circumstances will change; and we shall find far too much to do in setting ourselves against the common enemy, to have either leisure or heart for contentions among ourselves.