Why do Ryanair allow me to book connecting itineraries through a third party, but not through their own website?

Yesterday I booked trip to Rome.

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I found this journey through Skyscanner and booked it through Kiwi.com.

Before booking with Kiwi, I tried searching the same flights up directly with Norwegian Air and Ryanair, to see what the prices were there. With Ryanair, I could not find the flight at all. Ryanair told me they do not offer any flights between those cities. They still tell me that.

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While researching for this question, I found out that I can actually find the individual legs of the flights on Ryanair.com, just not the whole CIA-OSL stretch. The thought occurred to me that perhaps they want to avoid selling the whole journey on a single booking, so that they are not liable for missed connections, etc, but it seems to me that whatever they gain from that should be way less than the lost revenue from not offering the trip at all?