>>91821271"Tumblr demographic"
You mean Tumblr shows, no? Because /co/ has always liked "Tumblr shows", since before Tumblr even existed, see Avatar way back circa 06. /co/ still loves shows like Danny Phantom and Invader Zim which were probably the earliest examples of Tumblrbait cartoons, before we had a word to pin down that whole demographic.
MLP is basically the opposite of Tumblr, it's autist bait, indeed such a grand storm of autismo that, well, /mlp/ exists now.
The biggest "evidence" of Tumblr crossposting on /co/ are through Honestuck's /hsg/ and Steven Universe's /sug/, but honestly it's not out of line with what /co/'s existing tastes are.
There's more evidence of Reddit crossposting on /co/ (and all of 4chan) than Tumblr crossposting. /co/ and Tumblr share interests in some areas, but there doesn't seem to be actual people who come here from Tumblr to shitpost.