I guess ogre isn't a one man project ? I believed he started by himself. It's different now. I think Ervin did the same for his Bullet physics engine or some other guy who creted jiglibX. it's juste a rendering engine plug to a game framwork you can do whatever you to it so there isn't a big deal if the guy is alone since He has done the most of it. Also the engine is using a code almost identical to xna. Plugin it to any game is easy and it don't reies too much on his hidden classes so you can adapt it to your need. And just to be clear the team is small but this is not a one man project. I've been part of the beta and they have been running for almost two year now which is cool.

I almost forget an example of a small team doing great, unity. they start at five and some people did they have taken the indie engine market in a couple of year. So yeah some project fails because creator aren't really serious but it's not always the case. I could mention a lot of companies build with ten people trying to do a game engine and then just drop the project for no reason.