It was overkill. Remus left out the part he'd been told about Sirius laughing as he was hauled away. No need to talk about that. He'd just put him through hell. That little detail wouldn't change anything. It'd just make it worse. If Remus ventured to guess, the laughter was because of the absurdity of anyone ever thinking Sirius was capable of any of that.
When Sirius sank to the ground, Remus was right with him, kneeling across from him. Really, they ought to have sat down before they went down this path. Standing on shaky legs was asking a bit too much given what they were discussing. Having held all of that in for the past several months, Remus felt a little sense of release but he was too distraught right now to appreciate that some of the weight was off of his chest, and even then, it wouldn't feel right because now he had to share that weight with Sirius.
Remus' crying had slowed, but the tears hadn't stopped. Having to bury three friends, knowing Harry had been sent away, and the other person he held so very dear to his heart was being blamed for all of it really had ruined Remus. He didn't think there was any way to come back from the despair he'd fallen into. Honestly, the only reason he was still getting up every morning or hadn't just told the officials who snapped at him about being Sirius' accomplice for how much he'd defended him to just go ahead and lock him up to was for Harry. Even though Remus didn't know where he was or if he'd ever see him again, if Harry did ever want to seek out anything about his parents, then he owed him that. It was the least he could give James and Lily's son after everything.
There was a time after being told time and time again that Sirius was guilty when Remus stopped arguing. It never set well with him; in fact, it made him sick to his stomach and repulsed at the thought of agreeing with anyone about it. But he just didn't know how to prove otherwise and he was just so worn down that he stopped and retreated into solitude. A lone wolf, in the truest sense. But now, seeing Sirius, talking to him and recounting everything to him, it all just became that much more clear that there was no way Sirius could be guilty.
"I know," he repeated. "You couldn't -- you just couldn't have done it. I want to find a way to prove it, to get you out. To bring you home."