Chapter 315:
The Third Mizukage's decision to retreat so decisively was based on harsh realities. After the other villages suffered defeats, Kirigakure knew it couldn't take on Konoha head-on. With their base camp far out at sea, their supply chain was slower compared to the other villages.
Orochimaru killing five of the Seven Ninja Swordsmen was the final blow, the straw that broke the camel's back leaving Kirigakure no choice but to retreat.
Thus, the Third Ninja World War ended in an anticlimactic manner.
Even Orochimaru hadn't anticipated that defeating the Seven Ninja Swordsmen would have such a significant impact on the war. To him, their lives meant nothing. At that time, he had simply acted on a whim.
If he could kill them, he would. If not, he wouldn't bother.
Otherwise, with his strength and the cooperation of three Edo Tensei Kage, not just seven, but even eighteen opponents wouldn't have been able to escape.
As for the weapons dropped by the Seven? Orochimaru had no interest in them. His strength had long surpassed the need for such tools.
To him, it was merely a gift for Tsunade.
After defeating the Seven, Orochimaru returned to the Sound Ninja Village with Kushina.