The problem has always been that there's this wall with Tapastic that for a lot of people, is notoriously hard to overcome unless you've gotten some kind of boost. Perhaps from being featured or bringing audiences in from another place. It puts in a lot of focus on creators but not nearly as much on readers. this of course means as a creator you have a lot of options but it also means you have to put in much more effort to gain readers.
It's the exact opposite on Webtoons. It limits your actions as a creator but puts far more focus on assisting readers. This, along with Webtoons overall higher population, makes it much easier to gain readership.
It doesn't surprise me one bit that your series is doing so much better on Webtoons than Tapastic because I have a feeling you never got a real boost on Tapaastic. You've gotten about 70+ subs within a years time I assume because you were persistent with your work. You probably got that same amount on Webtoons in less than a week.
Until recently, gathering readership on Webtoons required far, far less effort than it did on Tapastic. Which is what worries a lot of people now. They fear that Webtoons is becoming a place where its no longer possible to gain easy readership as it was in the past.
Of course we all hope that this is just the typical sign of a slow month or two and everything will pick back up later. On that same subject,even I've seen some very slow positive improvements.
The sad thing is, you're probably never going to see much of a boost on Tapastic unless you get it via some way, again such as being featured or essentially getting up to the front page. The fact that you have posted the same material (spread out more over Tapastic in fact) but you've only gotten 4K views compared to the 180K views on Webtoons has always shown the fundamental issue of Tapastic.
That being how hard it is to even get attention. If it was just subs, you could argue that your series just isn't popular enough for people to want to keep reading. When your views are down though, it means people aren't even bothering to click on your icon to read our story. It requires a hell of a lot more effort to gain readership here. So again, it doesn't surprise me you're doing so much better on Webtoons. You should feel proud I think to make it this far on Tapastic on what I assume was sheer persistence.