First establish what the question is actually asking, does it want you to determine how important a factor is, or does it want you to determine the different factors at play.
Then, plan your essay, really you should be aiming for four paragraphs + intro and conclusion (but 3 might be fine for a B). These should all be distinct factors, rather than facts. Consider the different strands of history (social, economic, political) and whether a factor was more significant short or long term
In your introduction, briefly introduce your factors and present your overall argument, you want to make sure that this aligns with your plan.
For the body paragraphs, try and get at least 3 pieces of knowledge per paragraph and evaluate how important that factor is to the question, especially in comparison to the factor named in the question. Make sure your focus remains on the actual question asked and lines up with the line of argument you presented din your introduction.
For the conclusion, essentially give a super quick summary of why the factor you have chosen in more significant that the other factors, in particular the factor in the question - don't introduce new facts here- and finally, answer the question that was asked, eg the factor in the Q was / wasn't the most significant.
It might be worth asking you teachers where they think you're dropping your marks - is it knowledge or is it exam technique.
As for model answers, I'd say ask your teachers if they have any you can look at, or try an look some up online.
The only other thing I can really say is make sure you are strict with your timing, you should absolutely not be spending more than 45mins on one essay. I do this by working out how much time I have for each paragraph (but the first one is usually slightly longer for me, just bc I have more to say) and sticking to this.