Sollozzo
1. Sollozzo was piling on, the flattery on Vito and Tom too
2. Sollozzo inwardly feeling smug that the Corleones have no idea about Barzini connection that it was Barzini all along
3. My take, Sollozzo / Barzini strategy was to let Tom discover the Tattaglia connection, hoping Tom would then stop digging deeper
4. Tom obliged!

Tom
  • Tom not digging deep enough to unearth the Barzini connection with Sollozzo's narcotics trade deal
  • Tom obviously stopped when Tom unearthed the “always a pimp Tatt” connection and looked pretty pleased with his Gotcha! handiwork when Sollozzo said “My compliments”

Vito
Slip-up Vito's worry was for the wrong reasons “finding out what they had under their fingernails” whilst Barzini, Sollozzo and the other families were plotting to kill Vito

Sure thing Vito “was complacent, careless” in “Not identifying Barzini” as the force behind Sollozzo and Tattaglia even “after the attempt on his life” which never could have happened unless sanctioned by Barzini, second in the pecking order “waiting in the wings to become Numero Uno”

among others,
  • the minting money Narcotics deal was just between Sollozzo, pimp Tattaglia and the Corleones
  • Barzini wouldn't want a piece of this lucrative deal?
    - 30% share alone should be three, four million dollars just in the first year
  • top narcotics man Sollozzo would just accept Vito's refusal No repercussions
    Sollozzo “I cannot allow another man to hold me back” from my dirty drugs business.... ah -- a little dangerous
    After all -- Sollozzo is not a Communist!
  • sending Luca over to Tattaglias “on that ridiculous [and suicide] mission” would “find out what they had under their fingernails”
    Corleones feared Enforcer, one man killing machine ended up Sleeping with the fishes
  • kept Vito's Under Boss Sonny and Consigliere Tom, totally in the dark about Luca's "ridiculous mission"
  • didn't up his personal protection
  • didn't smell a rat when Paulie was calling in sick
    interestingly, Paulie's Boss Clemenza didn't either
  • Fredo -- well -- Fredo was -- well -- his driver / bodyguard
    Fredo stayed in the car!

Vito, Dead man with or without Sonny's gaffe However Vito could have avoided being shot Five times by not buying oranges!