Prior to writing an answer to this question students will need to organise their thinking. These factor cards might help.
Ask students to think of different ways in which to arrange the cards to create a pattern that might help shape their answer to the question. If they lack confidence and need a few ideas, how about:
grouping long and short-term
grouping economic and political
grouping Gorbachev v other factors
linking BIG ideas with smaller pieces of supporting evidence.
The way of sorting factors that you hope they will go for is prioritising. This is why the cards are diamond shaped, so they can create a diamond 9 ranking shape with the most important reason at the top, next important coming below etc.
The spares are for students to add ideas they think are missing. This should be done during the activity, rather than before and should arise naturally. Some students will simply say “What are these blanks for, Miss?”, but others may think that the factors offered provide a necessary but not sufficient explanation. You would hope that more able students would be confident enough to provide some supplementary factors of their own.