Yes sometimes tribes are not careful about who they give rights to
It is more likely that someone wanted to do it who was in the tribe and wants to remain anonymous.
Probably, they have created a random dummy account, invited the 'player', given them rights and done it by proxy. They have done it quick when other players are off line or asleep. Probably done in a matter of minutes. Not enough time for other players who had rights to go check who sent the invite or take back the rights. So i am guessing the other players with rights got kicked first.
I am also guessing that they are unlikely to have kicked themselves from the tribe. This is like those pyromaniacs who set fire to things and then have to hang around to watch the devastation. Nobody would do this and then remove themselves from the situation. They want to see what happens, watch the forums and the chats, cut and paste the convos etc
So if i was you Birdy, I would look at your list of players getting kicked and see who had rights and who was NOT kicked and if you can remember, anyone who did not donate much. Players who are going to throw it away very rarely contribute unless they have to.
Obviously i don't know it is pure speculation, but i find this more believable than hacking innogames. If they can get into innogames they would be diverting money and obtaining crowns not messing about with one tribe. They would do this to numerous tribes not just one.
I don't get the pure hatred that some players have for others. Everything should be forgotten when you go on new worlds. This is a terrible thing to do imo.
Players have spent money on this. It is mean-spirited to do it this way. Beat them the proper way using your time, knowledge and skill effectively. This is nothing to be proud of.