Ogre had its golden period at the time when game engines were becoming so complex that writing a complete engine from scratch was definitely becoming too expens

Ogre had its golden period at the time when game engines were becoming so complex that writing a complete engine from scratch was definitely becoming too expensive for small teams to take on and the major engines at that time still had very high price tags attached (e.g. something between 500k $ and 1M $ for UE2 or UE3 for a single title). Turn-key engines were only slowly establishing themselves (Torque had a pretty bad reputation, Unity was still in its infancy...). In this situation, the a reasonable thing for many small studios was to cobble something together from parts that were available: bullet, Ogre, OIS etc. There was barely any out of the box tooling for these libraries and I doubt that many teams invested a lot of time to write custom editors that were better than barely workable for their immediate project. This situation ended when Unity took over. Compared to all the half baked in house solutions, its all in one package with all the painstaking integration work was pretty attractive.