MC admires popular girl at this point but it's clear that it's not romantic, that he has no interest in dating her, just being able to carry on the sorts of ordinary social interactions she manages so (apparently) effortlessly. He sees that shy girl has it even worse and offers to work together to overcome their shared issue. He also thinks she wants his friend and, for the first time, isn't against being the middle-man facilitating something like that -- partly because of his recent experience as a love advisor but also partly because he realizes she's a really sweet girl who wouldn't be a bad match for his incredibly popular but completely inexperienced pal to finally find love beyond the hardwood.
Shy girl also admires the way her CF is able to interact with others but, at this point in the story, hasn't overly indicated any romantic interest in the MC. Even through LN2, by which there's no doubt she's hot for the MC to the point where she's only mildly freaked out when the risk of a video call while bathing pays off story-wise, we still don't know why. Her feelings clearly predate the trigger for popular girl's, but that's the extent.
Popular girl is at this point interested in MC, mostly as a pivotal figure in her outlook on life thanks to his tenacity as a permabenched hoopster in middle school who got exactly one chance to show what he could do at the end of his career in a meaningless garbage-time appearance and gave it 2000%. She wants to get closer to him to thank him and befriend him -- at this point. A lot of things will happen from here and relationships will change, grow and even, occasionally, move backward.