I've said it before, but Mike Pence actually once had a fairly good chance of becoming President of the United States, certainly a better chance than almost anyone else ever gets.
Immediately after the January 6 insurrection, there was a brief window of time when even Republicans were outraged by what happened. Both members of Trump's cabinet and Pence himself talked openly about the possibility of evoking the Twenty-Fifth Amendment and removing Trump for mental incapacity. In those few days it looks like there was actually a chance it could happen.
Then the moment passed. Within a week, Republicans began minimizing January 6, and the serious talk about the 25th Amendment was shut down when Pence ruled it out on January 12. At that point, Pence's chance to be President was over, and he is almost certainly never going to have that good of a chance again. If Pence's ambition is to serve as President, he blew it, both with his initial indecisiveness when Republicans were most likely to go along with a Trump removal, and then when he ruled it out entirely on January 12. Because of those decisions, there will never be a President Pence.