There are three things that would prevent a lawsuit the way I see it.
1) None of the copyright owners of Bluey become aware of this even existing in the first place.
2) Even if they are aware this exists, they may not want to do anything because they dont want any association with something ABDL or remotely nsfw related. They ARE a kids show, after all.
3) Even if they are aware of it and they dont think addressing it would be more of an issue than ignoring it, they may not have enough (or any) financial incentive to do anything about it. It's not like tykables putting something that looks like Bluey on their diapers is eating into the market of the owners of Bluey. They are targeting kids and their parents. They are making a television show, and at best they would be merchandising things like cups, plates, lunch boxes, pack packs, stuffed animals, etc. MAYBE even Bluey printed baby diapers. I cannot imagine for a moment that they have any intent on expanding that to adult diapers. In short, they are not directly being hurt by this due to competition related loss of revenue, and as long as the general public doesnt know about it and this whole thing doesnt blow up into a big fiasco that somehow makes them look bad, it isnt directly hurting them by association either.
Technically of course they could make a claim for intellectual property reasons, since they own the rights for it. But I dont think they would see it as a worth while action.