A thing that is not told on this thread but is mentioned in the history:
Croats were living previously to their migration somewhere in North of Romania, in the SW of current Ukraine land.
Now, in that area there is plenty of I2-din.
I do not think is mentioned how much time Croats lived in that area, but a very plausible hypothesis is that White Croats took I2-din from that area, North of Romania.
To whom this I2-din belonged, well to the Thracian-Gothic population that was there and which very likely was Slavizied.
Croats were living there and moved because of Avars during the Slavic king Samo, which seems to have been of Frankish origins.
Croats revolted against their Avar masters but were defeated and Byzantine Empire gave them the permission to settle in current lands of Croatia, as refugees. Otherwise, is possible that Avars would have killed lots of Croats.
Later, Serbians migrated also and they occupied land Eastwards of Croatians, because Croatians took the land more Westward, as they migrated passing through current Hungary lands.
I think is quite common sense.
A thing is that Croatians could have already taken Eastern Balkan admixture from Thracians-Goths mixed which they assimilated North of Romania.
https://en.wikipedia.org/wiki/White_Croats
This info comes from Nestor chronicle but also from the Byzantine kings.
Samo is not legend, he actually existed.
So no, Croats are not here because Roman Empire did not protected these lands, but because they were saved and granted land by the Byzantine Empire.