What happened to international distribution of S3-S4?

[AMJF]

When the DVDs of the English language version of Mysterious Cities of Gold S1 sold well, it triggered renewed interest in the franchise, enough for Chalopin and Deyries to make S2 to S4, set in China and so on. While there was an English language version of S2 available on DVD in the UK, after that, interest seems to completely evaporate in releasing S3 and S4 in the UK, let alone America.

So what happened to make S3 and S4 only available in French (AFAIK)? Were the S2 DVD sales not enough? Or did the French want to keep the show for themselves? There was an English dub made of S3 which I luckily caught and enjoyed, but S4 was harder and was in French only with English subtitles, but that was the end of the show at that point, and a sense of closure for the characters.

I just wish I could've owned official versions of the DVDs, but looking now for the French S3 and S4, the rarity is through the roof, with ridiculously high prices! Did the momentum for the show stall completely? Did everyone lose interest in Mysterious Cities of Gold, or was the story, for most, considered finished in S1?

It's a shame, because it was a great set of follow-up seasons to a classic first season, which was for decades, the only one.