They have researched it, the report started out finding that
ecig were much less harmful than cigs and had proven success in reducing smoking rates. It then concluded that ecigs must be restricted. Yeah I know. One of the contributes to the report distanced himself from the conclusion when it was published so we can assume that was tacked on after the report was sent to whomever commissioned it.
The minister then read the report (you know, skimmed and skipped to the conclusion, we all do it) and proposed the law change.
It's politics not science or police work.