This is all about implying serious work and complexity is taking place for some interaction there the user thinks there should be some.

PayPal used to have an entirely artificial five second wait between the user hitting "log in" and the browser sending the request because it raised perceived security in user testing.

Many banking apps will display "establishing secure connection" for a while for the same reason.

(Possibly paypal still have an artificial delay, but it's hard to tell given how badly the site works these days)