It's rare for Alfin to find information that is alien to him. For someone of his stature and background, it was not odd for him to be aware of most of this world's secrets.
But learning that the alien that stopped the war on Taurus, was also the one that started it. Now that was something juicy.
Yes, it was pure entertainment to him, a history lesson of a bygone era which had nothing to do with the present. He didn't know those that died, nor did he experience the harsh world they faced.
Because the world of today is much worse than before. To the current populace, the bygone days are something akin to heaven, even if it was rife with conflicts.
It's why he didn't care. But it's not like he can't understand Reina here, what she might have felt at that time. The desperation to stop the destruction of the world when no one listened.
Still, at the end of the day. What happened before doesn't give Reina the right to put the lives of people of present in danger.