It’s a given that any member of either house will have a variety of motives affecting how they see and do their job.
But bear in mind that the overwhelming majority of legislative business, in either house, is set/driven by the government, not by individual members. Committees are chosen in relation to the balance of the parties, primarily. Some measures may come forward from the concerns of individual members, whether as discrete initiatives or as amendments to government proposals, but they’re not likely to get anywhere without ministerial support or at least acquiescence. And of course, personal financial and material interests are supposed to be declared.