What is the cause of citta?

Hello everyone. What is the real cause of the chain of moments of citta: the previous moment of citta or the kamma that gives birth to a new chain as a result?

HI Nikolay,
you are asking about the causes for the succession of cittas that has no known beginning and that will only cease at khandha parinibbana.
To fully reply to this would take the full Patthana- last book of the Abdhidhamma - which explains the 24 paccaya, conditions.
Nina van Gorkom’s book gives a readable summary : https://abhidhamma.org/wp-content/uploads/2022/05/The-Conditionality-of-Life.pdf

In brief yes, the previous moment is one of the conditions for the next moment. However that alone is not sufficient. Each moment has a number of conditions.
See the Vism
CHAPTER XVII The Soil of Understanding (conclusion): Dependent Origination

also

Dispeller of Delusion p.181

  1. For here there is no single nor multiple fruit of any kind
    from a single cause, nor is there a single [fruit] from multiple causes,
    671.but only multiple [fruit] from multiple causes.* Thus from the multiple causes, called temperature, earth, seed and moisture, fruit
    called a shoot having visible form, smell, taste, etc. is found to
    arise. But |148| one representative cause and fruit given thus: “With
    ignorance as condition formations [arise], with formations as condition consciousness” has a meaning and it has a purpose. For the
    Blessed One uses one representative cause and fruit when it is
    suitable for elegance in teaching and to suit [the inclinations of]
    those susceptible to being taught. [And he does so] in some instances
    because it is a basic factor,38
    in some instances because of obviousness and in some instances because of being not shared.

I swear I wrote that before. But I guess that was a quote from me anyway.

Yup:

A way to think about this

If patisandhi citta does not arise, later arising cittas will not arise whether it be vipaka, kriya or kusalākusala.

It should be said regarding patisandhi citta,
it is produced by past action (kammato pana nibbattattā)

The fact that our kusalākusala cetana not just makes an effort regarding whatever current action but future bhava as well is a profound matter. Avijja is a sucker for punishment.

For an Arahant who has eradicated avijja and tanha, there are are no reasons for any kamma to come forward in producing a new patisandhi. That is the end of mind.

This is not to say that cuticitta is also necessary as anantara, vigata etc cause.

But Arahant cuticitta is not an anantara, vigata etc cause. It all ends right here.

idañca dukkhaṃ nirujjhati, aññañca dukkhaṃ na uppajjati