It's simply not true. It has been debated amongst Christians throughout history and continues to be until this day under what circumstances abortion is allowed. And it's also worth mentioning that church's official positions on moral issues are there to act as guidance for their members, they are not necessarily something they believe should be imposed on wider society. That's why you can still buy pork and alcohol in almost all Muslim countries despite literally every Muslim scholar agreeing that consuming them is a sin. So is banning pork a "Muslim position?" No, it's a
conservative position, held by people who seek to impose their religious beliefs on everyone else.
They were attacking the Catholic (not Christian) church on a whole host of issues related to feminism, because they saw it as a threat to women's emancipation. Choice over abortion was one of these issues that they identified as an important area where the Catholic church held back, as they saw it, progress towards these ideals. Evangelicals got involved because they saw feminism as a threat to wider Christianity.
The point of that post is to mention that the vehemently and vocally anti-abortion churches of today were actually very late to the party, and shared the view along with plenty of other churches Again, what you're doing is basing your view purely on who shouts the loudest, not what the huge range of churches and Christian scholars actually think, which is of course far more varied and nuanced.
The Wikipedia article
Abortion and Christianity highlights the many varied and nuanced views that Christian groups take on the issue. The vast majority do not have a blanket opposition to abortion. And it's worth mentioning again that an official position of a church is there to act as guidance for its members, it is not necessarily there as an indication of the laws they want to impose on everyone else.
However, the pattern that comes up again is that
conservative members of whatever particular sect of Christianity are more likely to oppose legal abortion in more circumstances. So what are you left with there? The realisation that conservative religious people are more likely to vote for the conservative political party. Well no shit. And that's why, despite him clearly not being religious in the slightest, they vote for him, because they share a far more important value with him: authoritarianism.