He mentions but does not address one of the main problems: sharing passwords is actually ADVANTAGEOUS to the politicians because it provides plausible deniability. Troy says "this is exactly the problem" (which is true), but provides no proposed recourse.
Looking at other industries, the problem goes away when people are held responsible for activities performed under their credentials even if they DID share them to other users. But it is particularly difficult in politics to hold people accountable for their actions.
I don't think that Troy Hunt can reasonably be expected to address the issue of "plausible deniability". He points out that is an issue, I believe it's on the organization (in this case parliament) to find a solution.
Personally, I'm all for the position that if you shared your password with someone then you are wholly and completely responsible for their actions. That is, the porn downloaded with your account is your porn, regardless of who actually was using your login to view porn.
Looking at other industries, the problem goes away when people are held responsible for activities performed under their credentials even if they DID share them to other users. But it is particularly difficult in politics to hold people accountable for their actions.