Well, let's study this issue a little bit. The problem is that the Golovin High Chiefdom is not able to check Hungarian expansion eastwards. It has Gavelkind succession, which means that many times, it falls apart after the death of the first chief (rarely there is only one kid or Kabuksin manages to switch to Primogeniture). At other times, the chiefs all declare independence from the high chief and Hungary can grab the counties one by one. Even if they stay together, the Golovins' only hope against Hungary is Cuman assistance, but the Cuman Khanate tends to be unstable as well, and even if they manage to assist their Pecheneg allies, Hungary can simply invite an ally of its own (Poland, Croatia, HRE... plenty of eager Catholic realms nearby). It's a snowball effect, and if Hungary starts expanding, it won't stop. Is there a way to simply reduce Hungary's eagerness to start holy wars somehow? Otherwise, solutions like the piety cost may help but also bring up other problems.
Its not the problem of weak Golovina realm, the problem is that there is no fixed AI relations between catholics / tengris, just like it is done with orthodox / tengri and orthodox / romuva and orthodox / soumenskuo, other religions / west africans. Look careful at the political map while playing CK2+ - orthodox duchies, and ERE, even when are very strong, attack pagans very rarely, only countries in east and middle europe that are aggresive towards for example batlic pagans or tengris is Poland and Hungary.
#slow down holy wars between pagans and non pagans
OR = {
has_global_flag = shattered_world
ai = no
NOT = { FROM = { religion_group = pagan_group } }
piety = 200
}
OR = {
has_global_flag = shattered_world
ai = no
NOT = { ROOT = { religion_group = pagan_group } }
piety = 200
}
#avoid invading west africa
OR = {
has_global_flag = shattered_world
ai = no
AND = {
culture_group = west_african
FROM = { culture_group = west_african }
}
AND = {
NOT = { culture_group = west_african }
FROM = { NOT = { culture_group = west_african } }
}
piety = 300
}
#avoid invading east africa
OR = {
has_global_flag = shattered_world
ai = no
AND = {
culture_group = east_african
FROM = { culture_group = east_african }
}
AND = {
NOT = { culture_group = east_african }
FROM = { NOT = { culture_group = east_african } }
}
piety = 300
}
#big grey blob
OR = {
ai = no
has_global_flag = shattered_world
NOT = { has_landed_title = e_hre }
piety = 300
}
#orthodox AI should avoid holy wars for the most part
OR = {
ai = no
has_global_flag = shattered_world
AND = {
NOT = { religion = orthodox }
NOT = { is_heresy_of = orthodox }
}
FROM = { religion_group = muslim }
piety = 400
}
#tengri AI should avoid holy wars for the most part
OR = {
ai = no
has_global_flag = shattered_world
NOT = { religion_group = eastern_pagan }
piety = 400
}
#jewish AI should avoid holy wars for the most part
OR = {
ai = no
has_global_flag = shattered_world
NOT = { religion_group = judaism_group }
piety = 400
As you can see (and if im not wrong

) these addons in holy war CB type (from common folder in Ck2+ mod) prevent orthodox realms from blobing into tengri, and other pagans lands. Im guessing thats why we see baltic pagans surviving so long, and rarely see ERE blobing east to the steppes. If I understand correctly, they need very big amount of piety to do holy wars. But there are no anti - blobbing measures for catholic realms like Hngary and Poland, thats why Hungary, without any higher requirments go all the way to the east.