Well, I'm not a mind reader, so I can't really give you any more than my opinion, based on watching this whole debacle unravel. First, there is a substantial contingent of both Labour and Tory MPs who support Brexit (or at least, there was). I would imagine that party whipping encouraged some to vote against their better judgement as well. When you say "went to the country", I assume you mean the general election, which May called, and led to a hung parliament. Labour gained 30 seats and the Tories lost 13, I think. I think they did have an intention to deliver it at first, but the complexity of the task, the dire economic impact and the unravelling of the lies from people like the ERG and Farage and his right wing cronies made it clear that it was not as straightforward as first imagined. May made some commitments that later proved unpalatable, and, as the country saw what was happening, they too began to change their minds. Rational people do that, in the face of new information.
I am much of the same opinion as you on our politicians: they have let us down outrageously and I can only read articles now: I can't even listen to them on the radio, they make me so angry. They have been appalling - lily-livered, duplicitous, self-interested and more. But unfortunately, we are where we are, so my interest is in how to prevent odious worms like Farage and his friends "Tommy Robinson", Banks, Bannon and the European far right from getting anywhere close to power: I don't want my granddaughter to ask what I did to prevent fascism, which seems to be heading our way, and having to say, I did nothing.
Hope that answers your question.
Multiple polls now show that more people support remain than support leave, though the gap is small and mostly seems due to leave supporters becoming "don't knows", rather than joining remain, though there is some suggestion that some leavers have changed their mind and now support remain. As I said, new evidence/information throws different light on things. For example, if you planned to marry someone and had got the dress and booked the venue and invited the guests and then discovered the person was already married, or dangerous or something, you would, presumably, change your mind.