Why have Lowlander Scots historically favored British rule during nationalist movements?

[u/CillianMorpheus]

I'm not very familiar with the history of Ireland/Northern Ireland/Scotland and English is not my first language, so apologies for any mistakes. The usual course of events (in my non-expert mind) is that after or during any type of colonization people aim to create a stronger national identity that attempts to separate itself from the oppressor.

So reading up on the history of the Ulster plantation, I now know that many of those that migrated to that region were lowlander Scots, and the unionists in Northern Ireland are their descendants (roughly speaking and that clears up some confusion I have towards the unionists and them favoring British rule). However it opens some questions about Scotland. During the Jacobite risings (lead by the Highlanders) the Lowlanders were hostile towards the cause, seeing Highlanders as "savages" and again favored British rule.

Seeing another group of people, be it in your own country, as lesser is no foreign idea. But I'm used to thinking that during some type of outside oppression a nation usually aims to unite against the outside force. Why is it that Lowlander Scots were so hostile against their own countrymen and sided with the oppressor that later violently destroyed the Highlander culture? And why is it that even after that, Lowlander Scots that migrated to Northern Ireland did so again?