I thought the more usual practice throughout history was "we don't care what those other weirdos want, we want their land".

I'm not convinced. Proselytization — and even forced conversion — seem to have been a less violent alternative to the previous human habit of killing all the adults and boys, taking the virgin girls as rape slaves, and eradicating the culture of "those other weirdos" when a military advantage can be had.

Moses was angry with the officers of the army [...] who returned from the battle. [...] "Now kill all the boys. And kill every woman who has slept with a man, but save for yourselves every girl who has never slept with a man." — Numbers 31:14,17-18

Human cultures used to be pretty good at "let those other weirdos do what they want, as long as they don't bother us" until certain proselytizing religions came along.

That's just not true at all.

Look at studies of warfare in "stone-age" tribes, e.g. in the Amazon or New Guinea. It's low-intensity but pretty constant.

Or look at the Vikings. Or the Mongol horde. How do you think the Roman Empire got so big? Etc, etc.