That is an interesting contention. But it could also have been a tactical one where weapons were put to better use than previously. It is very difficult to prove without more data though.

If I am not mistaken though this is the time of the rise in prominence of the longer swords, call them what you wish.

In your Viking invasion of Ireland those would be axes and welded swords as well as some tactical developments, the way they used their shields and stood in formation. That coupled with the early Irish disdain for metal armor would account for the rapid Viking expansion there, though it did not take all that long for the Irish to emulate and to some extent stop any wider expansion even if they couldn’t or wouldn’t expel the invaders.

Obviously for a people to expand their territories they must be militarily or diplomatically successful.