Izuna & madara were said & shown to have been
the first to awaken the MS NOTE that they were the first & not the only ones,yet it was said that they were few that got these power(MS) but it wasn't said that madara & Izuna were the only one with MS,
now u might say why can't it be that d brothers were the only ones that had the MS why? becoz if it was only madara who had the EMS & everyone else had normal sharingan then HE alone would have killed all the uchiha's with ease in a night like itachi & tobi but he didn't, why would a god at that time listen to some old weak uchiha's when they should be worshiping his EMS
Only 2 reason can be given,either they were up to 7 uchihas which he knew that together they could kill him or He had sometin someone he cared about.
Now i doubt that 20 uchiha's can take madara even with MS,he will only use a meteorite to kill everyone but if u were to look at it that madara had someone he cared of & that person was not powerful enough to fight for himself or herself,so he had to agree to the uchihas then he later left the village to get this person he cared about out of harms way,Now the only person that madara even cared about was his brother & as far as we know he never had a wife.
This would explain why he 1st left the village then before fightin harashima
Now to why tobi in this case Izuna is doing all this in the present,Izuna was madara's best friend,brother( & if i may add lover

)since madara did not die at the end of the battle it is only Natural that he would go to a place where he could try & treat his wounds,
Now u might say even if izuna was there how would a blind person take care of a dying Madara but what if he was not totally blind,madara izuna & kakashi are the only Ninjas that have unlocked their MS without killing their close friends,