There was a time where translators seemingly got free reign in translating whatever they wanted including titles and character names. A lot of them got weird variants like that: Schtroumpfs/Smurfs (definitely get why they did it for this one), Spirou/Robbedoes , Tintin/Kuifje, etc.
I agree that in many cases they went too far, but there's examples where it made sense to translate a character name if they were a pun of some kind (Asterix has many examples of that happening).
As for Suske en Wiske, those names aren't just very Flemish, they're basically very specific to the region around Antwerp (I don't even know what their non-diminutive names are supposed to be). I don't love the translated names, but it does make sense to make them more 'normal' sounding for other regions.