I will say these two things as someone from Canada over the supreme court decision in the U.S:
Exactly why would this happen now? Of all times you would think it would have happened in the Bush Jr. Era back in the 2000's considering how neoconservative he was.
The second thing is how Canada and the U.S swapped views on abortion. In the 1980's the Canadian Prime Minister almost had it banned from existence losing by just one vote in the Canadian senate to put it back in the criminal code. Where as the American President (would have bern reagan of course) didn't seem to have much interest in banning it and seemed to let it be. Now the views are reversed.
Explain.
The votes just weren't there on the Supreme Court at any other time. And abortion reform had to come via the Court because they were the ones who put in place the original abortion decision in the '70s that stated governments can only ban it in the last 2/3 of pregnancy because the infant would be "viable," or capable of living outside the womb. If an abortion case came up before now, it would be likely that the Court would have tried for a compromise, because there were always some conservatives who weren't willing to rock the boat and some liberals who approved of the original case. They actually did another abortion case that stated the government couldn't make it too hard to get an abortion, because states were choosing to shut down abortion centers for other reasons, and the Court said they had to keep them open in many cases and make them easy to get to. So you can see how it kind of went from "you can't BAN it" to "you have to almost actively support it."
As far as why a case has made its way up to the Court, with states outright daring them to overturn Roe by passing laws that went against it, it's a multitude of things. The pro-life movement has only grown since the '70s, partly because ultrasounds are so good now that many areligious people have become pro-life and can't see it as defensible on any grounds. As the science has gotten better in defining when a human life begins and when it can be saved (even if delivered prematurely), the pro-abortion side has had to adjust its arguments in ways that are unpalatable to most people, who want to believe it's a heart-wrenching decision for the woman and is only done when necessary. They don't want to hear people bragging about how many they've had or how technically there's nothing wrong with abortion at any stage of pregnancy, even when it's clearly just got to be C-sectioned out and it will be fully born.
You could also argue that the "my body, my choice" slogan got co-opted by anti-vaxxers, so people were kind of like, "Oh, I don't have to take this seriously as an argument because liberals don't seem to apply it consistently anyway."
Roe basically supercharged the argument and cemented it in such a way that we couldn't argue about it or make incremental changes in either direction because the Court took it out of our hands. The effort has been in putting justices on the bench who believe you can only rule on what's in the Constitution (abortion is not), not whatever the Court thinks. If they believed that, they were pretty much guaranteed to rule against Roe if it ever came up because of how weird the original ruling was.
Compare the US' laws to Europe, and you can see the same difference. Most abortions in European countries are limited to 12 weeks at most. In the US, Roe set it at something like 24 or 28. And did so before ultrasounds were invented. And without tying it to any medical milestone, just what "felt" right and fair. So Europe has been able to make uncomfortable compromises as voters, whereas the US has had to patiently lay a lot of bricks into place before we were even allowed to have this fight. So it at times looks like both sides are just using it to drive votes, but that's kind of because the efforts were always going to go through the slowest branch of government to get their outdated compromise rules taken off the books. The debate is going to be incredibly volatile because any incrementalism was taken out of our hands and now it's all built up and will get nasty.