not religion but the basic inability of humans to too often fully pull together. It's great that we are not bees in a hive, but that leads us off into our own personal beliefs and actions that do not support the group, and often tend to trash it.
Just three of those groups...
One group, essentially social, that had no particular aims but was based on, shall we say, a personal condition (think along the lines of "bald Headed Men of America" . It had a vague stated aim of service, but ended up almost destroying itself in internecine wars. Never once was it mentioned how these usurpers or other evil types were going to further whatever aims we had, but either the old order must be abolished or the newcomers raised to power. No peace or accommodation could possibly be allowed.
Another group, essentially supporting scientific studies, had a similar revolution because certain people out of power simply hated those who were running things. The fact that they existed was the problem, and every little thing was blown out of all proportion. (Very similar to the first group) Secret meetings were held, the villains were expunged, and the organization went back to being a sleepy little thing out in the middle of nowhere.
The church I am thinking of was previously split almost in half by a former minister who had this Trumpian ability to sow strife wherever he showed up. He was eventually shown the door, but not before leaving a very bad taste in everyone's mouths. We had ex-Catholics, Jews, atheists, homosexuals, and various races all getting along in a Peaceable Kingdom-- until it wasn't any more.
The thing these three groups had in common were nebulous goals and being run by volunteers. Hate to say it, but unless everyone in the organization has a stake in it, like a paycheck, it's herding cats times 10. Not impossible, of course, but on very thin ice.