First of all, you need to keep in mind that our community consists of people, and people don't always act consistently. With borderline questions it can often be a matter of luck which questions the community lets open and which it closes. Everyone's personal decision if they vote to close or not can be influenced by appearance of the question, current mood, group-think mentality (already got 2 close-votes, maybe I should VTC too) and other factors. We should all try our best to decide objectively and independently what to close and what to leave open, but unfortunately nobody is truly immune to subconscious factors affecting their judgment.
But if I look at only the rational factors, then the difference between these two questions might be that the second question asks about "What is [politicians] positions on [issue]?" while the first asks about "Why is that [politicians] view on [issue]?"
Questions about political views of someone can usually be answered by citing public statements or pointing at past actions a politician took.
But if you ask for the motivation of a politician to follow a certain agenda, then you run into the problem that you can not read their minds. We can never truly know what a person thinks. Maybe it's truly their believe that it is the best course of action? Maybe they have a personal interest in the issue? Maybe they are representing the interests of a well-donating lobby? Maybe they are pandering to their voter base? Maybe there are party-internal reasons? Maybe it's a strategic stance they just take so they can give it up in exchange for a concession on a different issue? Maybe they are mind-controlled by aliens? Without reading their mind it's impossible to tell what their true motivation is, because they would never admit any reason but the first while on record. All we can do is speculate. And speculative questions are usually considered primarily opinion-based.
What you could ask, though, is "What reasons did [politician] state for taking [position] on [issue]?", as this can be answered by citing statements they made. Whether or not to believe these statements is up to the reader.