Because Felix Talked To Him!! - Tumblr Posts
When Oliver engineers his meetcute with Felix via the pin in Felix's bike tire, he finds Felix sitting under a tree, uselessly spinning the flate tire, and claiming to already be 10 minutes late to his tutorial after skiving off the whole past week.
And I just think this offers several really hilarious possibilities.
One: Oliver's "plan" was so spur of the moment that he doesn't even know Felix's course schedule, he has probably been skiving off his own lectures to stake out the bike shed and/or ride frantically around campus in the hopes of actually being there to "rescue" Felix next time he takes his bike out, and the fact his "plan" somehow succeeded was way more sheer dumb luck than clever planning on his part.
Two: Oliver's been watching Felix enough to have a good idea of his class schedule. With luck that only an Oliver could manage, however, he stuck the pin in Felix's bike tire right before Felix started skiving off that term. Now Oliver has been riding up and down the path between their dorms and Felix's tutorial all week without so much as a hint of Felix, had already biked up and down that path a few times the day they finally met, and was close to giving up on the bike plan entirely while trying desperately to think of how else he could engineer a meetcute, when he finally ran across Felix who had definitely set out 10 minutes late to tutorial in the first place and had only been sitting under that tree for like one minute, tops, when Oliver found him, and Oliver was just so excited that his plan had finally worked that he happily ignored the part where Felix cares zero percent about his classes but still uses the, "Oh, woe is me, however shall I salvage my school work, kind stranger?" act to get Oliver to fix his problem for him when Oliver stops to talk to him.
Three: Felix is lying about having skived off the whole previous week and possibly lying about being 10 minutes late to his tutorial, too. In fact, Oliver finds Felix sitting uselessly next to his broken bike exactly when he expected to find him. However, Oliver is still so excited that his plan worked that he absolutely does not care what nonsense Felix is making up about skiving and being late and whatever, who cares, Felix is noticing him and talking to him and Oliver is Doing A Plan and It Is Working, and Felix literally doesn't need to try so hard to convince Oliver to help him because Oliver would help Felix with literally anything Felix wanted, even if he hadn't kinda sorta 100% completely been the reason Felix even needed help in the first place.