From a birds eye view, it looks like TikTok is boosting new users content and it also looks like fake engagement to me. Why would percentages fall off a cliff after you go over 50K followers?
Not true for IG, depends on content. I’d bet if you tracked 27K IG profiles you would see a gradual decline as some big accounts still have crazy engagement. The above graph is pretty obvious TikTok has fake engagement.