I've dubbed a new leadership principle based on the 300s church controversy called Donatism. The principle is this--God can do great things through an evil leader. Sometimes I hear people say that a leader will fail if his or her heart is not right with God, or God won't bless a ministry if the leader's motivations are wrong. There is a sense sometimes that the most important characteristic of an effective leader, especially in the church, is that he or she be spiritual.
Certainly that's ideal. Certainly you can't have a leader who embezzles or leads a church/company in an immoral direction. There is basic ethics. But there are gobs of spiritual people who will just as soon tank a church/company because they lack leadership or management skills. And there are lots of spiritually mediocre people whose leadership skills are off the charts.
The Donatist controversy was over priests and such who had caved in during persecution. What if that immoral bishop had baptized you and then you find out he's a scoundrel? Christians decided that it wasn't the character of the priest that legitimized the baptism or communion. To put it in my words, God is the one who legitimizes your baptism.
In the Bible, we have the example of Cyrus, king of Persia. Not a chance this guy believed in YHWH. But God used him to restore Israel, even calls him God's anointed (Isa. 45:1). So God can use even an evil guy outside the church to accomplish his will. That's the Cyrus principle.
But I'm not talking about people outside the church. I'm talking about Christians who are effective leaders but who aren't known for being great prayer warriors or for fasting a lot and who may at times be a little unpleasant while getting good things done. God can and frequently does use them.
There's a flip side to this. Apparent success doesn't mean God and the pastor/leader are best buddies. A large church doesn't mean this guy or gal is praying five hours a day. It may actually be that we should expect to find the most spiritual people more in the nooks and crannies of the church, not up front.
The ideal is of course someone who is both an effective leader and spiritually minded.