Unfortunately this is part of the cynical calculus of geopolitics. Russia and China can't be seen to be siding with "gangs", and they won't go against a major global south country like Kenya which they hope over the long term to turn to their side (integration into BRI and so on) and which is more valuable in terms of resources, economic power, military power and geopolitical sway in their region than tiny Haiti. They also want to maintain an image of being always on the side of upholding stability in other countries and not encouraging domestic conflicts, as this image also helps them to be well regarded in the eyes of many global south governments who are very worried about instability in their countries and want to know that they have partners on their side who will help them maintain stability regardless of the nature of their regime. This is meant to establish a stark contrast with the West which promotes protests, riots, color revolutions and general destabilization of society in countries whose governments they disapprove of.

In short, as long as the official government of Haiti, as comprador and corrupt as it may be, approves of and requests this sort of action (even though we know it was really orchestrated by Washington) then it would go against China's policy of not intervening in other countries' internal affairs to stand in the way.

I don't like it any more than you do but i don't see a way for Russia and China to stop this which would not be viewed poorly by most of the global south governments that they are trying to court right now.

It is not the same as the Libya situation because in Libya Gaddafi's government was the officially recognized one and it had not asked for a UN intervention.

In fact on the surface this is more akin to what Russia did in Kazakhstan less than two years ago when they came to help the Kazakh police forces suppress riots and what was likely a western attempt at another color revolution. Of course i say on the surface because the form may be similar but the essence is diametrically opposite. In the one case it was a suppression of US orchestrated instability, in the other it's the suppression of popular uprising against a US backed comprador government. The long term effects will also be very different. Whereas in the one case the intervention forces pulled out almost immediately after finishing their mission we know from past experience that the imperialists in such cases usually intend to stay as long as possible, acting as a very brutal occupation force. If they can get away with it they would like to stay indefinitely just as they tried to do in places in Africa where they ostensibly went to "fight terrorists" yet somehow the situation never got any better so they always had a reason to stay.

The reason being of course to keep the comprador regime in power that will uphold neoliberalism and austerity and enable the imperialists to continue looting these countries, continually bleeding them dry of every cent of profit from cheap labor and every dram of natural resources.

Russia and China understand this but they can't do much to stop it at the moment. Haiti is too deeply embedded in the US sphere of influence. Their calculation is probably that over the long term the best way they can prevent this sort of thing from occurring in the future is to continue helping the global south to escape the neocolonial underdevelopment trap by building up their infrastructure and their productive capabilities, which will take away the West's leverage over them and allow them to act with more autonomy on the global stage.