[an amused spectator]

The linked article doesn't indicate that he was taking it as a preventative, as joesbucks contends: "I go back to Phil Valentine who was using Ivermectin as a preventative."

Just that Valentine had found a doctor who agreed to prescribe Ivermectin. It appears that was AFTER he'd contracted Covid:

After Phil Valentine tested positive for COVID-19 but prior to his hospitalization, he told his listeners to consider, “If I get this COVID thing, do I have a chance of dying from it?” If so, he advised them to get vaccinated. He said he made the decision not to get vaccinated because he thought he probably wouldn’t die.

Phil Valentine also said that he was “taking vitamin D like crazy” and had found a doctor who agreed to prescribe ivermectin, a drug primarily used to treat parasites in animals.

The "also said" is apparently part of the radio conversation from the preceding paragraph.

I haven't been able to locate a story saying Valentine was taking Ivermectin preventatively.

[Steve Van Doorn]

said, " “taking vitamin D like crazy”"
That is sad. Vitamin D alone isn't going to save you. I wonder if they gave him an anti-bacterial. This is the thing most people are getting killed with. Largest malpractice that is on going in the history of the world

[joesbucks]

He was taking Vitamin D and Ivermectin as a preventative. Not as a treatment.