I think a lot of what the author said can be true as well as what I said.

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I think you're smooshing together three ideas: ritualized warfare or sacrifice, spreading the influence of a particular religion through warfare, and spreading a particular religion to all the conquered peoples.

For ritualized warfare or sacrifice, you don't necessarily need the victims to believe what you believe, you just need them to die or be conquered. "I don't need you to believe, I just need you to die."

Back during bronze age Mesopotamia, every city has its own patron deity, and it it wasn't typical for religion to be spread through warfare per se.

Even much later during the Islamic conquest around the 7-8th century, the Islamic caliphate was grown through warfare, but in fact Islam was a religion of the ruling class and because Muslims were exempt from certain taxes, and were given additional protections by the religion and so it was contrary to the interests of the ruling class to have the ruled follow the same God.

So for this second thing, it's "I don't need you to believe, I just need to be your King who believes"

It really wasn't until the axial age monotheistic religions and particularly much later Christendom that you wanted everyone to necessarily join your particular religion, likely because it stopped being a way to feel in control of a world that's too random to fully understand and became a social code for people to agree on and live by to reduce the stress of having to deal with a bunch of people you don't know in big civilizations. In the East, multiple religions often coexist because they each were compatible with one another and provided something important, such as imperial China balancing Daoism, Confucianism, and Buddhism, so monotheism isn't necessarily mandatory for the axial age social technologies to work, it just happened that a particular strain ended up highly successful in the West. Essentially, "I need you to believe what I believe, but you can believe other stuff too."

Judaism really didn't want converts per se, but it did demand exclusivity for those who did believe. It was a regional religion for people of a certain bloodline. Some people did convert, but it was never an evangelical religion even being Abrahamic. Christianity's innovation was opening the faith to anyone who was willing to convert, combined with the enforced monotheism of Judaism (or to be more accurate, the precursor to Judaism from around 0 BC). The combination of the two did make it a lot more aggressive than the polytheistic faiths that preceded it.

So in this final form which Islam also inherits, it's "I need you to believe what I believe, and nothing else"