Many were at it before. Iran had a war with Iraq, Russia had destroyed Chechnya before Iraq or Afghanistan. What’s changed is that USA is declining its influence and these regional powerhouses are expanding their influence and unsurprisingly they are worsening things, because there are things worse than the west. Now Iran can fill the vacuum, like it couldn’t before with sanctions, and use its proxies to spread its Islamist ideals and Russia can exert influence over what it sees as its regional influence to the detriment of the lives and sovereignty of those in it.
As for interventions working, it did with Kosovo, Timor Leste and Sierra Leone. Lack of intervention in Syria has allowed Iran and Russia to spread their influence and over 500,000 civilians dead.
