It bugs the mind to think that places like Ulster, who only a few centuries ago started to adheer to protestant schools of thought, after a brutal campaign against their own kin, whilst Scotland, who hath been on the eyes of the anglo saxon lords for a considerably longer period of time, with raids deep into the heartland starting with King Edward up until the ascenscion of James the I; son of the deceased Queen of Scots, and a believer of Lutheran values, and with the already meager and decentralized Scottish Catholic base crippled with the deaths of powerful nobles such as Hutly and Knox's successses in contributing to the enactment of the Scottish Reformation, how's it still remain in fact, that the Scottish populace at large overwhelmingly cling to the Holy See? Was there a lack of fidelity by the Nobles to enforce Lutheran values onto even the folk of the Scottish lowlands, or is there perhaps a more intriguing and or insidious reason?
It didn't.
Scotland was overwhelmingly protestant at the time of the Acts of Union and while there was significant Catholic presence in the Highlands this was reducing and after the failure of the 1745 uprising it was largely eliminated during the cultural crackdown.
Catholicism in Scotland almost entirely stems from large scale Irish immigration during the 19th century, hence significant Catholic popultions are only found in urban centres.
But today this is increasingly irrelevant as Scotland is a majority non-religious country.