But the follow up question is whether a man can be a Christian believer without being filled with the Holy Spirit. And this is shown to be the case.
Paul met several congregations where they had been baptized as believers but had not yet been filled. Were they fair game for demon possession?
IIRC, that particular group had received the Baptism of John and said they didn’t even know there was a Holy Spirit. So technically they weren’t Christian until they believed the Gospel of Jesus Christ and Paul laid hands on them.