The door-taping thing was pretty standard fare at the time --the occupants of the Watergate themselves would do it on occasion. Howard Hunt was greedy, stupid, and corruptible. Plus he had ties to Nixon-run operations going back to the mid-Fifties.
Although why McCord taped it the SECOND time is pretty suspect --but these guys were pretty cocky, thinking they operated under the aegis of executive protection.
@countZZero