Yes, they believed they'd shatter the TS Magnus, but collapse is completely different, so they're still picking it, and the team trusted him with that hero. That's one of LGD's mistakes; they should've respect ban on Magnus, and I think it's a bad decision to display their awesome draft (lycan tiny) in the battle between team secret; perhaps team spirit already knows about this draft and is preparing for it. I checked Team Spirit's recent matches, notably in the Easter qualifiers, and they've managed to stay in the upper bracket, indicating that they're more than just a normal dota2 team.
They did become confident that they can beat Collapse's Magnus again. If I were their coach, I'll respect it and will ban it for the entire series. Although there really are heroes that can counter Magnus but it's still going to be different from most of the games if there's a comfort hero that has been banned. As I've read xinQs post in weibo since there's an issue that's rotating towards their coach, he said that even they'll ban Magnus, Team Spirit, all of them, have a large hero pool.