I don't really have a dog in this game, I hardly knew who Schweizer was before Doha. And I was myself surprised both by her performances as well as Houlihan in 2018 and Purrier at Millrose and similar cases.
I think there are two aspects here (and both have some relevance for speculations/suspicions I don't want to insinuate any, though), namely "sudden improvements" and apparent large differences between performances in different events. The second point first: Obviously there are different types of runners and while one can perform well from 1500-10000 or with an even wider range, most runners will be comparably better at one distance. The 3k is a special case because it is the distance where real long distance runners meet the middle distance runners (and steeplechasers). Furthermore, it is special beause it used to by the main track distance for women in the 1980s and early 1990s but now that's the 5k. So we have O'Sullivan and other runners from that time with comparably better 3k times (her 8:21.6 would be worth well sub 14:30 but her best was only 14:41) whereas nowadays the 5k or 1500m times are usually better because there are far more opportunities for peak performances over these distances.
Now contrary to the way it usually is, Schweizer got the opportunity for a perfect 3k before she could show her improvement in the shorter or longer distances, let's just wait for summer, if it was an outlier or if she can match it. (Cf. other runners with 3k "better" than other events: E. McColgan: 4:01 8:31 14:46; L. Weightman 4:00 8:26 14:44. As Schweizer is more of a long distance type than Weightman, she might not get to 4:00, but she might run low 14:30s 5k.)
Improvement is expected when people are turning professional. Schweizer had already an 8:41 indoor 3k (and 4:27 mile) in early 2018. So she improved 16 seconds in two years in the 3k. In the 5k she wen from 15:19i in early 2017 to 14:45 in Doha via 15:02 in 2018, 34 secs within more than two years, almost evenly distributed. Her 1500 PB is from 2018, so this obviously does not reflect the improvement, but 3k and 5k are in the same ballpark.
Houlihan 5k: 2016: 15:06 2017 15:00, 2018 14:34 AR 32 secs in two years but to a better mark and at one year older.