This has been pondering my mind lately did Obitos survival really get explained?

I mean all we know is that during Kakashi gaiden, Obito push Kakashi out the way of a huge boulder and saved his life, but Obito whole body was crushed in the process (though normally a boulder that size and weight would kill a person in a instant). Obito gave his right eye to Kakashi and his left eye smashed in by the boulder, plus those ninja used earth ninjutsu and buried Obito with more rocks. Obito the conveniently landed in front of Madara hide out. Madara said Obito "happen to slip threw", but I don't buy that lol.

So what are your guys thoughts on Obito's survival?

What it a good enough explanation or what it BS to you?