>>46820090I think it's a gross exaggeration to call it a tantrum, he just looked extra pathetic because he'd just been knocked over. He raised his voice for all of two seconds, immediately calmed down, and admitted his feelings were dumb and selfish. That is more emotional maturity than most people ever show for fuck's sake. It demonstrated that he had conflicting desires: He wanted Mikasa to be happy, which he knew she couldn't be with him, but he also wanted Mikasa's love. He chose to outwardly reinforce the former while still retaining the latter.
About Ymir, anyone with half a brain would have seen it coming. We already knew she married Fritz and bore him several children. Do you really thing old King Fritz could have raped the original founding titan, or forced her to do ANYTHING against her will? No, numb nuts, she wanted his dick. She could have taken over as queen at any time. Is it a little fucked? Sure, but you shoulda figured she was fucked in the head after grinning at Mikasa making out with a disembodied head.
About his mom, at that point his thoughts were starting to become a mess. He quite explicitly stated that they were becoming incoherent and implied he was experiencing everything at once. We've already seen that older Eren could be seen by previous advancing titans. He was following a plan, a slave to something he's not even sure he himself laid out.
Armin and everyone else are thankful because they finally understand Eren's true intentions. He didn't want to kill people. He didn't want to be a bastard. But he allowed himself to fall into the role, with the belief that it'd be best for all his loved ones in the end. He loved his friends and family enough that he was willing to become a monster for them, even as it destroyed him to do so. His willingness to take on an unforgivable sin for their sake.
He freed Eldians from their genetic curse and gave Paradis a fighting chance at survival.