No doubt to keep the story rolling, threads going, keeping the board active!
It caught Sollozzo's attention that Sonny was hot for his deal

Good point Turnbull The reasonable inference is that he couldn't get the million which was just finance for Vito, from Tattaglia yet as you say if they had a million dollars or could guarantee why couldn't Sol have gotten it from them?

slippery and dicey Sol says I'll take care of the Tattaglias, outta my share What is their contribution that deserve this generosity?