You need to use better sources. I see a number of untrustworthy sites here, and just a Reddit post (entirely unreliable source). Also seeing a lot of straw man arguments in what you’re saying.

Try to have some nuance; the world isn’t divided into two clean sides, and multiple parties can have hostile stances towards each other at the same time. That does not mean “the enemy of my enemy is my friend” if that enemy of your enemy is also attacking you. For example, the US killed ISIS-K’s leader back in 2015; not a friendly maneuver. (Source: https://www.reuters.com/article/idUSKCN10N21L/ )

Now, Russia has actually done a lot to earn this terror group’s ire; we have the history of the Tzar’s trying to conquer Afghanistan, the Soviet Afghan War that took 10 years in the 1980’s and was Russia’s Vietnam with a massive civilian death-toll and the destruction of vast amounts of infrastructure, the wars and oppression in Chechnya, the heavy support with Russian boots on the ground for Assad in the Syrian Civil War against the civilian rebels, the ongoing extreme violence and repression of Muslims by Prighozin’s Africa Corps, and the now the forced mobilization of Russia’s ethnic minorities (many who are Muslims from Central Asia) to fight in their morally bankrupt genocide against Ukraine. China has plenty of pressure points with ISIS-K too; chiefly the ongoing Uighur genocide, hence the attacks against Chinese officials in Afghanistan.

Turns out if you do decades of terrorism against a people they might do it to you, regardless of if your country is considered “East” or “West”.

China is more unusual, but the Islamic world is not a simple, singular thing. Religion can be hostile to near faiths. If catholics are burning protestants(or vice versa) I wouldn't thinking making friends with one, would endear you to the other. Even if you are friends with the Taliban, Isis doesn't really care. To them the Taliban aren't pure enough. No one but them are. Reaching out to the rest of the Islamic world may be seen as a negative to them.

If they are next to China, and china is not them, that may be enough for them to justify it to themselves. Religious extremists don't tend to make perfect sense to people who see the world as it is.