It's an ANOVA study of a cohort of 613,602 pediatric patients aged 10 to 19 years between 2020 to 2022 based on electronic health records that include factors such as vaccination status.
It reports the correlations found - those that had a COVID diagnosis (with no prior diabetes indicated) had a greater chance of developing diabetes.
It doesn't report that those vaccinated (with no prior diabetes indicated) had a greater chance of developing diabetes NOR does it report a great many other potential relationships.
The probable reason for that lack of reporting is the absence of pattern being present in the data ... it's reasonable to assume that multiple correlations across fields in the EHRs were run (including against vaccination status).
If you suspect a vaccination effect you can always look to Australian health studies - the country has decades of world class near total population records for the entire country and had a near total COVID vaccination program with multiple doses.
Any effects would clearly show up in the before and after M&M stats of 25 million people.