Good question my friend, to begin you need to look back to see what connection anime has to trannies, firstly there are many traps in animes including Astolfo, Ferris Chan, and many others. The connection that trannies have towards anime is related to the trap fetish itself, many "men" came out as traps when traps started to become popular a few years back, due to this they believed that they as with the 2d boipussi husbandos could be passable as something to stick your dick into, this level of delusion soon escalated, many trap fetishists began saying "Traps dont exist in a 3d realm" to mock the massive influx of feminine "girls" often insulting and ridiculing them.
To begin on how they got to where they are today, after the "why wont these closet trap loving homosexuals love me with my horribly unpassable appearance" era, they began to migrate to sites like patreon, tumblr and others to accumulate a following, the reason? they wanted to make money and gain attention like e-thots do.
For Example:
http://img0.thatpervert.com/pics/post/full/shemale-cosplay-Shemale--poison-5395780.jpeg
In conclusion, just faggots taking opportunity by the balls.