1) You have no idea if animal ivermectin supply chains overlap with human and you have no idea if or where there is a bottle neck. Odds are quite high that there is a predictable use of ivermectin for animals and there is an increased demand due people buying it unneeded, which has caused then shortage in otherwise stable market.
2) Ivermectin isn’t a CDC recommended remedy to Covid. So, while some doctors may still prescribe, that doesn’t explain greatly increased demand
3) You can always throw conspiracy theories at the wall and hope they stick, but you need evidence if they are going to be considered anything more than conspiracy