To add what Tilver said:
According the Constitution, specifically the Twenty Fifth Amendment, when there’s a vacancy in the Vice Presidency, the President nominates a successor who is then confirmed by Congress. The Amendment was passed during Lyndon Johnson’s Presidency; prior to that, when a Vice President resigned, died, or was elevated due to the death of the President (by assassination or illness) the office of Vice President remained vacant, with either the President Pro Tempore of the Senate (until 1947) or the Speaker of the House (after 1947) being next in line, with the other after that. Then came the Presidential Cabinet in the order the departments were created.
After the Amendment was passed, it was only used twice, both in the same term: in 1973, Vice President Spiro Agnew was indicted for bribery and tax evasion; when he resigned from office, President Nixon named House Minority Leader Gerald Ford as the new Vice President, and Ford assumed office after being confirmed by Congress. The next year, Nixon resigned because of Watergate, and Ford became President. Ford nominated New York Governor Nelson Rockefeller, who was confirmed by Congress as the next Vice President.
tl;dr: If President Biden stepped down, Vice President Harris would become President, yes. But Pelosi would not become Vice President, though she would be next in line until President Harris’s nominee for Vice President was approved by Congress. Granted, Harris theoretically COULD nominate Pelosi, but again, as Tilver suggests, Pelosi’d probably decline.
whos not smart enough or qualified to do the job.
Oh, I can think of some people that Harris is much smarter and more qualified than. Some of them have even had the job as President as recently as early last year.