I'm normally the last person to side with defensive players before attacking ones, but an experienced player who has previously paid her dues at the venue concerned & wins the 1st set then is up 3-1 & serving in the 2nd set and then once again is up 3-1 & serving in the 3rd set facing a rookie who is has significantly more talent than tennis brains, has few excuses losing that match.
In light of said pov, I have to disagree with the notion that Ostapenko won purely on the basis of her own merits. Halep's play on her own serve at the end of the latter 2 sets was atrocious: broken 3 straight times to end both those sets, yet she held 7 of her 9 other service games? In short, she lost every service game that occurred with the finishing line in sight, but she held the overwhelming majority of those which took place when the finishing line was still well off in the distance? That suspiciously reads like how one would spell the word c-h-o-k-e. She played to her ability when the pressure of finishing the match off was at bay, but then lost 'chunks' of games when it was present: those service 'stat facts' suggest nothing short of her having frozen under pressure, which is obv. nothing new for her in Slams the last 2+ years. Ostapenko can (& did) hit winners willy nilly, but she can't dictate Halep making a 1st serve or not, or dictate where she might direct a 1st or 2nd serve (to the body or either wing). There are numerous other observations I might make, but there's no point and I've highlighted the key one. Halep got the breaks she needed at the beginning of all 3 sets, but the moment the title got within sight Ostapenko just magically happened to get so much better that Halep couldn't live with her. That magic didn't happen in a vacuum.