If you look at your argument and apply any pragmatism then there is no way a true conservative (that you represent Will as being) would endorse Biden and Hillary.He advocated lower taxes and then seized up and agreed to a lower tax pittance. He insisted he would veto any spending bill he didn’t like, then signed the budgets as written. He said he would end our wars but cowered in the face of resistance. He unilaterally started an all out trade war with the test of the world (including our allies like Germany) saying it would be easy to win and would reduce the trade deficit. The exact opposite happened and as things got worse he doubled down on his mistake. He said he would build a wall and make Mexico pay for it, then confiscated money intended for the military. He said he would reduce the number of regulations businesses would face, implemented a plan to do it, then quietly backed it off.
Your question is precisely why George Will is so anti-Trump. Many, if not most Trump supporters think he is a conservative because he talks bad about liberals and the left. But he is as far from being conservative as most liberals. He is a mercantilist, nationalist state capitalist (fascism light) who is just as on board with big government as the left. Will left the Republican Party because it became Trump’s party which means it eschews conservative principles and replaces them with big government MAGA principles. He recognizes that the ascendance of MAGA will set back small government conservatism for generations to come.
Trump said he'd veto spending bills he didn't like. Yep. And he didn't. So instead, Will endorses a candidate that wants 3.5 TRILLION in additional bloated spending.
Trump said he end our wars. He didn't end them. He reduced our troop counts, stabilized the region, and negotiated multiple peace accords between Arab states and Israel. But he didn't pull out the final 2K troops from Afghanistan. So instead, he endorsed a candidate that voted for every one of the wars, and when pulling out, managed to turn the entire country (including billions in military hardware and financial aid) over to a terrorist organization.
He unilaterally started an all out trade war. Eh, sure he did. He applied tarriffs which you are against and renegotiated NAFTA. Given the 3% national unemployment rate he achieved, sustained market growth, all without the unbridled inflation of the current administration, I'd argue his trade policies seemed to work. Well, up until a man-made virus was released and wiped out all his progress.
He said he would build a wall and have Mexico pay for it. Unfortunately, Congress and the courts blocked him, so he tried his best to work around it. So instead, Will endorsed the people who prevented Trump from performing his 'conservative' action of securing our borders and then once they took power, literally opened the flood gates to what might be the largest human migration of all time.
So based on this analysis there are only two possible conclusions: Will has the intellectual capability of a 6 year old, who roots for his enemy because he didn't get exactly what he wanted from his supporters, or Will is paper conservative who actually endorses liberalism and its causes.