Because the fun stream is set to the Automatically Approve memes that appear to be SFW option. It’s basically an algorithm that determines whether you posted any key words or not like profanity, slurs, and whatnot. If an image has any of the key words that Imgflip is looking for, it’s sent to the stream mods for review, otherwise if it doesn’t have any key words, it is automatically approved. That’s also why you’ll sometimes find non-political memes in the politics stream, the algorithm approved it.