It took 19 months of broken promises and belligerent rhetoric for Hungary to finally ratify Sweden’s entry into NATO.

Why all the foot-dragging, many observers wondered, when Hungary was going to approve the Nordic country’s membership of the military alliance anyway?

That question has perplexed even members of Hungary’s governing party, Fidesz, according to Peter Ungar, an opposition legislator. He said he had been approached by one Fidesz lawmaker, in the run-up to Monday’s vote in Parliament to accept NATO’s expansion, and asked: “‘What the hell is going on with Sweden?’”

That a member of Prime Minister Viktor Orban’s governing party would seek an explanation from a rival politician is a measure of how puzzled even allies of the Hungarian leader, never mind his opponents, became over their country delaying NATO’s expansion.

“The whole thing is incomprehensible,” said Mr. Ungar, a Hungarian progressive whose mother, Maria Schmidt, is a prominent conservative and longtime ally of Mr. Orban. “Nobody understands what the problem was,” Mr. Ungar added.

He declined to name the member of Parliament who had sought him out, saying that Fidesz demands unquestioning loyalty to and acceptance of Mr. Orban’s decisions, no matter how bewildering they might seem. (The government did not respond to a request for comment.)