This works because almost all the US uses first-past-the-post elections for the Presidential general election. So you get outcomes like this:
Scenario 1:
Biden: 10 votes
Trump: 9 votes
Kennedy/Stein/West: 0 votes
Biden wins the state
Scenario 2:
Biden: 9 votes
Trump: 9 votes
Kennedy/Stein/West: 1 vote
Tied vote, decided by game of chance/lawsuit
Scenario 3:
Biden: 8 votes
Trump: 9 votes
Kennedy/Stein/West: 2 votes
Trump wins the state
This is why you see huge financial support from Republican billionaires for third party candidates who have no chance of winning.
It kinda makes them look even more short sighted tbh. Like yeah, you can look at “there’s a few polls where he takes from Biden” and call it a day, but it’s kinda missing the fact he’s lost a lot of relevance already with no signs of stopping.
It’s kind of a catch 22: he’s stealing votes from the low-info pool, but at the same time if he’s not defined at all he’ll make no impact by election day. Elevating him can fix that, but that risks those low info voters realizing what they’re getting into and then start biting into Trump’s numbers as expected.