So this doesn't work as a simple math equation because you have to understand a lot of key concepts first. This has basically nothing to do with the electoral college system so we will put that aside and start with the "first past the post" system of determining elections.

On it's face the First Past the Post (FPP) seems fair. Highest percentage of votes for a candidate wins. But imagine a system where we have a lot of parties. Say there are five- The red, blue, yellow, green and purple parties. So you have an election and maybe the spread looks like this :

RED 20%
PURPLE 25%
BLUE 15%
YELLOW 10%
GREEN 30%

So Green takes the election... However this doesn't actually represent the will of a majority as only 30% actually voted for green. So in our little Rainbow country, as generally happens the encumbant party makes mistakes or compromises and becomes less popular. So next time the election comes around you get some party consolidation. Blue maybe has enough ideological cross over with purple to merge into a new party. Yellow is say kind of an extreme outlier and Red and Green are close on the political spectrum but they really believe they got this. Let's say maybe some of the compromises in the new Blue/Purple merger turns off some of their base and Red snags some of their vote share this time.

The new spread looks like this

RED 25%
BLUE/PURPLE 32%
YELLOW 15%
GREEN 28%

So the problem remains. Only around 1/3 of voters actually chose the "majority" who takes all.

So next election let's say Green, seeking to snag votes does the same thing Blue and Purple did. They change their platform to be more like Red to court the votes of Red party people. The problem being is they are too similar. The next election happens and they end up tying with red because the two parties split the votes but that razor thin line of preference between the parties splits the share. This is called a spoiler. If RED and GREEN are decently acceptable policy wise to the voting pools of both voters then you have a group of 52% that represents what a majority desires policy wise...but that 32% Purple/Blue party is still in control.

So over time Red and Green merge. They win an election. Blue/Purple changes their policies and the two start trading back and forth. Yellow eventually dissolves from never winning and you end up with a two party system. Almost all FFP systems devolve into two party systems through histories that look like this.

Now say we end up in the situation we are in now. The two parties over time sort of naturally drift further and further apart as a branding initiative deepens.

Now imagine one has sown incredible brand loyalty. They are marketing experts, they have been hammering everyone's fear buttons for so long that they could run the literal devil and the party would still vote for them because to do otherwise is heresy.

On the other side you have what could be best described as the lesser of two evils. They don't have to be paragons, their entire strategy has been to be good enough while maintaining a status quo that benefits people like them but they treading water. They aren't fixing anything just adding time to the clock. Not great but probably also not going to sink the ship.

The two go head to head.

Under normal circumstances the voting share between them is pretty evenly split. But it will be a frozen day in hell before those carefully indoctrinated into the marketing strategy of the Right wing will vote differently. If they did they would have to admit they were wrong and well... Everything that's been piped to them for years has painted the other side as decadent, subhumans who are "UnAmerican".

The lesser evil has basically just run on being the lesser evil. Nobody was excited about voting them in last time...

So the votes happen.

38% Democrat
40 % Republican And the remaining 22% split between a series of independants.

If 3% of that 22% those people thought Trump was the greater evil but didn't vote for the lesser evil then their abstention to participate in voting for a lesser evil , or even just not voting at all basically enables the Republican win. It's not a vote for vote pledge to support Trump, it's a more complicated series of value judgements. A FFP system over times demands gaming of the system. That's why many places have ditched FFP and has these more complicated multiple voting systems to make governance more representive of the actual will of the people to stop this from happening.

America is stuck until that kind of reform happens.