God calls people for a season in life, that's how I look at it. Just as in any other ministry, each individual felt God leading them in another direction.
Let's look at an example on the secular side for me personal....(May not be a good example):
I went to school to be a computer programmer. I started out my vocation as a computer operator, went to Helpdesk, eventually reaching a programmer status. The economy changed my view on programming and I decided to go into other areas such as Tech Support, Web Design, and other platforms.
As poor as this example is, let me tie this back in with Petra band members...past and present.
Greg left the band to be more with his family at the time and later went solo. He currently has his own ministry, serving the Lord as He calls Greg.
Louie Weaver, despite the conditions of his departure, now has his own ministry going as well. My speculation is that God turned a "Why?" situation into a "That's why!!" situation.
Ronny, as stated earlier, left the band for personal reasons only to have his own studio. (By the way, he holds Petra in the highest esteem...check his website out at
http://www.ronnycates.com and read for yourself.)
These are just a couple examples of how big God's plans are versus man's/woman's. We may not see the big picture until we are in His arms but sometimes He allows us to see reasons why situations happen in our lives.
I was fortunate to see a portion of this through my dad's death. Questions like "Why did God take him so early?" soon gave light to some information. How much of an impact we have on others, what could have been if he stay with us much longer, and various other insights came to light during this time.
I guess I got a little long-winded (Comes from have three uncles as preachers!!) but it all boils down to this one statement:
God's ways are much better then ours. He has such a broader field of vision then we do!!
Sorry, I don't know if I got off the beat and path here.
Have a great day and fantastic eternity!!