The fact that Hamas can't control the flow of goods (and possibly money and people) across the borders of its territory speaks volumes. Either they are lying through their teeth or they are effectively powerless.
The latter case is contradictory with the notion of a government, so they must be lying.
(Note that this argument may also apply to the United States government with regard to illegal alien traffic across our southern border.)
Both are true. They don’t want to stop the smuggling & they couldn’t even if they wanted to.