Also, it’s a 100% fact that companies consider client rosters confidential. It’s fun to say no one can claim my name or phone number as confidential data… but that’s not how things work.
It is how things work legally. What you are confusing is the distinction between individual bits of information and a database: if a salesperson leaves and calls their old client, nobody reasonably expects them to forget about that relationship or be unable to look up a phone number.
If there’s an entire lead database, that might be a different story if it includes non-public data and the company can show that it’s treated as a valuable asset (limited access, confidentiality agreements, etc. ). If it’s something you could recreate with a few Google searches, you’ll have a hard time convincing a judge that there’s substantial value in its secrecy.