From this manga we know:
- Madara gave his sharingan to someone else - The guy who controlled 2nd mizukage
- Madara needed help and was fortunate obito was near his hideout
- Madara needed more sharingans
Madara used someone else apart from tobi and either this guy betrayed him or got killed.
By the time obito fully recovered the war was over and he probably saw rin die which is what made him change. He probably just wanted to help madara to get out of there initially but when he saw rin die he started to hate everyone and followed madaras plan.
Obito probably encouraged the uchiha clan to fight the leaf and then told danzo the plan so the leaf could kill the uchihas. part of the deal was danzo would get some eyes and obito the rest.
When sasuke meets obito at the hideout it shows obito has hundreds of sharingans.
Madara awakened the renigan and then gave it to nagato because at that time he was the only young uzumaki without any allegance to any groups then help them set up akatsuki.
Some of these theories i already mentioned before but no one agreed with me.