Sacking temples wouldn't have been a move to antagonize the Church, it would have been a move to mobilize the Church. If I was leading Niselur, and I wanted to destroy the Chuch, I wouldn't have sacked the temples either. It'd be a stupid thing to do.
Yes, the Terran fiasco had grave consequences. It was a bad move, and I never even suggested otherwise. Even I was opposed to it, but that didn't make me go attack Astrum. The elders' mistakes may have made cracks, but nothing forced Niselur to reform itself into a monarchy and to go ally up with Asylon and sack Astrum. And seriously, you want me to believe that Leopold was against attacking fellow astroists? Why the heck is that exactly what he did, then? He took his actions because that's what he wanted to do, not because he was forced to do it. He wanted to shake things up and make things more fun for the nobles of his realm, and the most geopolitically sound manoeuvre was attacking Astrum, which it had less affinities to and possibilities to expand into, and get in league with realms that were more to his liking, like Asylon, FR, and Phantaria. It suited his ambitions. He's not a victim.