The only issue with all of that is that Buddy mentions to Quinn that Vinnie is already doing a lot better than her. Why would he try to muscle into Quinn's business when it's tanking anyway?
Yea thats why Bill Gates still works out of his parents garage and Elon Musk still plays with his Lego ... Duuuuuuuuuude are you for real ? Rule #1 of any buisness : take out any and all competition ! The closer they are, the more aggressive you have to go about it. Buy em up, undersell their stock, offer the same products cheaper, make exclusive contracts with suppliers or distributors, if all fails tackle them at the knees, but you never ever stay put! The only thing your "oh im already making more, why bother" strategy is gonna get you is a surefire way to file for bankruptcy.
And Quinn is the most obvious target, they share the same supplier, anywhere and anything she has access to, Vinnie has too.
And everything else points to him and only him :
1. Cathy pic - She kicked him out of College.
2. Using DIK Laptop - he has insider knowledge and needs to get rid of Rusty, because Rusty wont ever let him deal out of the Mansion.
3. Trashing of Mansion - with the assumption that Rusty had to step down like Chad due to the Catchy pic, it makes them desperate for money.
4. Nicks room beeing almost untouched - his best friend.
5. Dude who mugged Quinn knowing when and where - if even Quinn wasnt sure when she had enough money, who else has access to that information ?
6. Riona feeling like she has been stalked - she is Quinns right hand girl, picks up drug drops.
Now if all of that is unrelated and a coincidence, well played DPC, but imo its very obvious that the last text message exchange between Riona and MC finally sets up the confrontation, like MC will shadow her, save her and then confront whoever has been stalking her and finds out all of it was Vinnie.