VCT Challengers Format?

How does this whole thing work? From what I understand, only the top two teams from Stage 2 playoffs make it to Ascension. If that is the case, what's the point of stage 1/midseason invitational? Or circuit points as well? If a team like Oxygen, who've only lost like twice all year, have a bad stint in playoffs then their season is just done?

League points are how you qualify / are seeded for playoffs, that why blinn finished stage 2 above m80/mxs/tsm but are the lowest seed in playoffs