It’s rare for a Rule 5 pick to work out, exceedingly so for a competitive team. There’s a reason that most picks were available to be chosen. The Rule 5 Draft happens once a year at the end of the Winter Meetings, and it allows teams to pick players from other organizations who are (a) not on the 40-man roster and (b) have been in pro ball for at least 5 seasons if originally signed at 18 or younger or 4 seasons if signed at 19 or older. The drafting team has to pay the original team $100,000.
The reason it usually doesn’t work out is that players have to stay on the drafting team’s 26-man roster for the entire following season.