You assume way too much... If you saved a "gang" in your neighborhood from being waxed by another "gang" in your neighborhood. After the bloodshed was over do you seriously think that the "gang" you just saved would just welcome you and your "goody goody" morals continuing hanging around "their" hood??? How naive can you be?
The Soviets take over Afghanistan. It’s another resource and labor. Not very hard to understand.