Just to be clear: I think Riot's decision regarding that situation is wrong.
That being said, the Guard did not sign the partnership agreement (in time). We don't know why. But whatever happened behind the scenes, the org decided to abandon the team, knowing full well that this could result in them not making partnership. The org tried to leverage their ascension win into de facto selling their spot (obv they can't literally sell their spot, because Riot owns the spot (one thing they've learned from league), but their goal wasn't to compete in VCT, it was to sell ascension winning players for high buyouts to an org that would take their slot). They didn't give a shit about the players and this result is something they knew would happen, and actively let happen.
Again, that doesn't mean that I believe Riot made the right decision here, but absolutely fuck the Guard for screwing over their players (and coach).