As I see it, three possibilities rise above the others:

• Russia is dusting off and refining plans that the Soviet Union made decades ago, and will claim it as a “huge innovation” or something like that, despite being a concept from the 70s or 80s that just never got off the ground for one reason or another. This could conceivably be done well under the right circumstances, but based on the incredible amount of manufacturing and production issues Russia is having as a direct result of Ukraine War sanctions, it might be that they can’t actually do anything without China’s help, because the highly specialized western equipment they’d normally use is no longer being sold to them, so they need a replacement supplier.
• Russia’s last moon mission went tits up fairly publicly, so Roscosmos is probably thinking they can avoid getting egg on their face if they can persuade China to unify their lunar base ambitions with their own. Note that this ignores the fact that China almost certainly wants to build a moon base entirely on their own, both as a matter of national pride, as well as the fact that they want to fully own any knowledge and expertise gained from such a mission.
• Putin is trying to entice CCP leadership to more closely align themselves with Russia in a geopolitical sense, as a more unified adversary to the west, which these days they both see as an implacable foe that they want to defeat. To me, this is the angle that would make the most sense in terms of convincing CCP leadership… but at the same time, remember that China is absolutely measuring Putin’s back for a knife at this point, because Russia’s got a shitload of natural resources up in Siberia that the Chinese would LOVE to exploit.