"That the leaders led in Israel,I have to admit, this is a little cryptic to me. I can't quite be certain whether they're blessing God for the people's faithfulness, or for His bringing the people together. For the first, they would be thanking Him for the victory they have been given, for everyone did their jobs properly. They had faith that God would see them through safely, and so they did their duties together.
That the people volunteered,
Bless the Lord!
The other way, they're thanking God for His direct influence in bringing everyone together. Rather than the people having faith, God worked directly on them to do their jobs correctly. I have to admit that in the current political situation, this idea would be very appealing. The leaders aren't leading the people? Hey God, whack them into shape and get them moving in the right direction. The people are apathetic? God, could you install some backbones right away? It would make for a much simpler, though less free-will, situation if God always pulled/pushed/forced people to do what He wanted them to be doing.