Samhain is not Hallowtide nor where Hallowtide originated - Christians honoured martyrs and other dead well before Christianity arrived in Ireland. I don't think I can convince you, but I would recommend reading the writings of churches over blog posts.
The connection between the two is largely an invention by some Victorians who tried to connect everything Christian to some pre-Christian 'purer' festival. There are several holidays people like to claim Christmas came from or Easter eggs that scholars fume and/or laugh about every year. We have a lot of writing from early churches on these things, they're just not as entertaining as Victorian tales.
The earliest we have about Samhain comes after the the earliest evidence we have churches in Ireland celebrating Hallowtide, and that early writing includes the 1st of November date. The idea that pre-Christian Irish celebrations would neatly fall on the Christian calendar is suspect, before getting the evidence that those types of celebrations varied with how well harvests and such went. It is significantly more likely that the later Christians writing those dates had them align with their local church calendars, especially as their Hallowtide dates align with other older churches outside of Ireland, meaning it's likely those who brought Christianity to Ireland already celebrated Hallowtide on those dates. I've not seen much on those writings that includes divination or necromancy, which churches of the time viewed as a type of divination - as you're aware from the Bible, necromancy involved raising spirits for information, not raising shambling corpses to do one's bidding as often portrayed today. That comes from different cultures others mentioned.
Yes, pretty much every festival ever is a fusion of local and cultural elements that change over time. The early churches had very little influence or control on how people did different holidays & by the time they did, those norms were well set. That doesn't mean Hallowtide originates in Samhain. It means like every other holiday, the way the Christian festival of Hallowtide is celebrated is influenced by the cultures around it and changes as culture changes. That's why it's celebrated in very different ways around the world. Pumpkins are combatively modern to the holiday, that only came around with Christianity going to the Americas, it's how festival change.
Just as Christmas brought in those Victorian ideas and became secular to many, so did Hallowtide, I'd argue even more so likely as honouring the dead is something is part of all traditional cultures and so expanded into wider culture easier and some of the tales the Victorians told are fairly interesting compared to honouring martyrs or church leaders wanting to separate out from the Jewish calendar and work out the date of the crucifixion and once happy with it then, because of Jewish folklore of Moses and similar having either been born or conceived on the same day they died as a 'complete' life, they just counted 9 months to get the day for Christmas. It's kind anti-climactic compared to stealing from pagans. .