>>12260228If you're looking for a serious/theological answer: Jesus washed his disciples feet, but they never washed His, because Jesus had no sins to [ceremonially] wash away.
The Pope claims to be the sinless vicar of Christ, in the place of, or anti, Christ. So he's doing the same footwashing, himself exempt, to convey that he's god on earth (he ain't). The kissing is to feign humility.