Sorry to break it to you, but women chose you not because you're suddenly more attractive than your friend, but because they've had 15 years or so to learn that your friend won't settle down and their biological clock is ringing real hard in their 30s.
Because among college men, the more senior you are, the higher status; also the single women of your age either date you or they date some guy younger(naah, women don't do that) or they date some guy outside of college(a bit harder) -- plus single women feel that it's "now or never" since it's the final year in college.
It USED to be be the same thing when you were in highschool before tinder and social media: as a male, the more senior the higher status you had -- i.e. 9th grader males will just drool at their female coleagues going out with more senior males, until in 12th grade you finally hit payday.
Not so anymore because tinder and social media allow females to reach a much broader male audience.
It's the same thing with women in their thirties -- they notice they get a lot less male attention -- first the bad boys stop noticing them and a couple of years later even the nicest of guys won't give them that sweet validating attention women crave, so the smart ones settle down with a nice guy in her early thirties, the not so smart ones end up basically cat ladies.
I think those are all fine points, but you said "women chose you" (me in particular) -- I don't think I disagree with the general trends you've laid you, but you don't know the individuals in my life, or their motivations.
In this situation, the man would be scraps... Wouldn't him? How would that make him feel? As someone unlucky with girls I vowed to never let myself become scraps for any woman when I get older.
It's quite cynical, I know.