Here we see that Obito succeeded in completing the Primary Objective of his Plan. He knew that extraction of bijju means death -
He Immediately went into the Leaf Village and summoned Kurama. And Kurama started doing his thing i.e. Destroying everything. But before that He saw Minato coming and taking Kushina away -
Focus on how he says Gone Again, No Matter. Now if his primary objective was to destroys Konoha he'd have followed Minato and made sure that he gets eliminated first but it didn't matter because his Mission was almost complete!
We know that Minato then came and sent a TBB away but Obito couldn't fight the urge to have a go at his sensei, I mean he came for Kushina and that's what the trigger was and that's why he attacked Minato.
Here we can see he wants to end Minato and that's why the Avenger-Obito speaks YOU will face ME!
We know how that Fight went. What I believe that 15 year old Obito with a Zetsu shell and newly acquired Kamui knew that he couldn't beat his Sensei and that's why his mission avoided fighting Minato [Plus there was a chance of Minato finding about his Identity as well] but the events that happened in the execution process triggered the fight.
In that fight Minato asked him whether he was Madara and that's when Obito spoke of Madara's Ideology -
After the fight Obito left with bold statements and no regrets [his mission was a success] but he also said that Minato deserves the title of the 4th Hokage.