Did this not happen in Merovingian times?
Mostly in the latter period and it was importantly related to Carolingian power-building.
Until the VIIIth century, there wasn't yet a fusion between titles, political power and landed benefices : they were increasingly associated especially on the periphery (Bavaria, Thuringia, etc.) were royal authority was more on a personal and remote level,but while giving in tenancy (due to the partial demonetarisation of economy) part of the royal fiscus to the militia in exchange for their service allowed them to take power from themselves instead of royal favour (which was really facilitated by the successive minority crises, allowing aristocratic and court shifts) you still had a distinction between
honores and
beneficii.
It changed with Peppinid/Arnulfids/Carolingians, which thanks to their redistributive role (as majordomii) could support their own clientele and oust opponents, needing to really boost their legitimacy and authority as a power-grabbing aristocratic family among other aristocratic families (where Merovingians had a special status).
It's not rare to see a Frankish (or associated, such as a Saxon or an Alaman) noble being trusted with functions and given land revenues in the other part of the realm, then being replaced by someone else, unrelated. Not that, again, you didn't have a growing confusion by the VIIth century, as well a broad regionalisation, but it was more contingential than an actual management policy.
This key difference might be one of the reasons why Merovingian Francia managed to last three centuries making do as things went, and why Carolingian Francia barely survived four generations, counting from Peppin II.
(Note that it was not a political absurdity for Carolingians, the Barbarian state inherited from Rome wasn't as functional it used to be, they saw an opportunity to overtake power and used means at their disposal to do just that. And they systematized a first form of what was eventually called feudality.)