Why did Yahoo change the "Answers" homepage and format ?

Because they like "fixing" things that aren't broken. They have a suggestion board if you want to try and voice your concerns there, but they seem to be fond of this "Just give it a try!" answer

the administrators are going nuts these days

It's a better user experience! We just added a blog with a video so you can take a look at the update: http://yahooanswers.tumblr.com/post/98750947217/yahoo-answers-new-navigation

Just give it a try!

Not sure,but if you want to use the other format just go to nz.answers.yahoo.com.