Odd that ‘gente’ is treated as plural here. Is this a mistake in the translation?
Es difícil enseñar a la gente lo que (ellos) no están dispuestos a aprender.
I am correct in thinking you’re saying that the original sentence is grammatically incorrect but some native speakers sometimes treat the word as plural?
I’ll mention that there is a concordancia section (section 4.7) in the RAE which describes when gente should be treated as singular and plural. It’s quite a long section so it can, apparently, be quite tricky to get right.