It's more likely the saturated fat, which red meat is especially high in. For example, saturated fat-driven weight gain results in a disproportionate amount of visceral fat gain relative to PUFA: https://diabetesjournals.org/diabetes/article/63/7/2356/3433...

> Both groups gained 1.6 kg in weight; however, the MRI assessment showed that the SFA group gained more liver fat, total fat, and visceral fat, but less lean tissue compared with subjects in the PUFA group (Table 2).

And even without weight gain, it seems to impair insulin sensitivity: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5291812/

> A diet very high in fat and saturated fat adversely affects insulin sensitivity and thereby might contribute to the development of type 2 diabetes.

No it wasn't, only relative to processed red meat:

> Over 5,483,981 person-years of follow-up, we documented 22,761 T2D cases. Intakes of total, processed, and unprocessed red meat were positively and approximately linearly associated with higher risks of T2D. Comparing the highest to the lowest quintiles, hazard ratios (HR) were 1.62 (95% confidence interval [CI]: 1.53, 1.71) for total red meat, 1.51 (95% CI: 1.44, 1.58) for processed red meat, and 1.40 (95% CI: 1.33, 1.47) for unprocessed red meat.