like said, its all about proxy wars man, superpowers know this, they known facing each other in battle will end really badly (like nukes), and will screw up their economy (economic bans can destroy countries that depend on other countries, like america and russia), so its far safer and better to let the poor people fight each other and then we go in and take the stuff we want.
thats pretty much the reason russia didint just took ukraine, the moment they tried europe came in and said "russia stop, or we will start economic bans" russia knew that would destroy them so they backed up, instead relying on fake rebels so nobody could pinpoint them.