This is a good question. Been wondering this for ages, and i don't know the answer.
I had a look at the stats there, and it seems Ireland and Scotland have had roughly the same number of cases (155k and 153k), yet Scotland has had over twice the number of deaths.
A higher rate of testing in Ireland doesn't explain it, as Scotland has completed more tests (3.6m to Ireland's 2.7m).
My guess would be Ireland has better shielded the elderly population somehow?