Crusader Kings 2: Bohemia campaign - The Vladimir problem

Pope called for the fourth crusade. Target: Jerusalem, for the second time. I was thinking how long would it take for him to do that because it was lost before Aquitine was lost and regained.
I had other ideas though: first time I asked to change to target on a pagan ruler that held land de jure of Kingdom of Vladimir, a kingdom that I was interested in because it forms part of the Slavic Union empire.

I was tempted to claim the title for myself as I thought it was possible to shoulder the -20 opinon from the Pope but negated by +15 for Crusader trait. However, I tried a different route that's inspired by my previous campaign: nominate a beneficiary who is father of one of my vassals. In this case, it was even better that the vassal was the beneficiary's only son, so that the kingdom would pass to him upon beneficiary's death and, I would think, it would fold into my realm.

Yes, we won the crusade and, due to early preparation and the short distance to the battleground from my realm, I contributed the most and so my beneficiary became the king of Vladimir. As expected, he refused to be vassalised (just one rank difference and I wasn't his de jure liege).

The good news was that there was no warning that his son's county would fall out of my realm due to succession and so I expect that upon his death, his son would take over (Vladimir's succession law is primogeniture) to become king and the kingdom should fold into my realm.

The previously described strategy didn't work: my vassal count inherited his father's Kingdom of Vladimir resulted in him becoming an independent king and even grabbed his county out of my realm. I did entertain this possibility because in my previous campaign, the same thing happend when a vassal baron inherited a kingdom. I was hoping that that it could be different this time because both father and son were of my dynasty. So my conclusion is that my vassals will remain as vassals if they inherit titles of equal or lower rank than their original titles.

I was in the midst of a war against France over a county when the above happened. This itself has an interesting story: decades ago, I tried to convert outisde pagan rulers by sending my chaplain there. Did it 3 times and in all of them, he was killed the next day by angry pagan rulers. I searched the internet and found out that it's difficult to convert them. However, it might be a little easier if they have the cynical trait, which the Luki's ruler had. First attempt didn't work, although the chaplain was allowed to stay for a while before being asked to leave. The second time it worked. Coincidentally, France's ruler left the Christian defensive pact and so I declared war on the nearby county where together with Luki and two other demense constituted a duchy. I hoped to capture this French county, create the duchy and then grant them to my vassal king, for ease of future conquest (ducal claim).

Problem was that something happened to the claimant (probably died) and so the casus belli became invalid. Stood down my armies and declared war again to gain neighbouring county, still within the same duchy, for my vassal. The funny thing was that while fighting this war, a vassal king finally pressed his de jure liege claim over Luki and won lol. All my hard work.

Bear in mind that my ruler had yet to exit the short reign penalty period. Raised some levies to fight France, twice back to back. Then noticed that Vladimir was in civil war. The rebels wanted to install the ruler's younger sister as their queen. I noticed that I could also press the younger sister's (both were of my dynasty, all due to me winning the fourth Crusade) claim to the kingdom and I hurriedly did it because if I win, she would be my vassal but if the rebels win, Vladimir would remain independent.

In my haste, I forgot that Vladimir was in a Christian defensive pact against me. I didn't realise that (I thought she was just calling her usual allies lol) until I saw the Pope's army. Eeeek. So at the risk of driving my vassal's opinion of me further down south, I raised all my armies.

Understandably, I'm really pleased at the outcome :) I could form Empire of Rus, for having 86% of the realm but I wouldn't do that. I am still gunning for Slavic Union. In terms of titles, I now lack only the Kingdom of Chernigov. Still got to complete Novgorod, Vladimir and Bohemia (damn Italian barony).