Because, I knew UTG was weak since he had openned 3 pots in a row and was sitting out at another one of my tables, so I was pretty sure he was just ending his session and wanted to use the last few hands to win some hands.

UTG+1 was a fish who cplayed 45% of his hands so I would've isolated him had he limped. Everone behind me was supertight, so unless they had a hand they would fold so I was rather confdent the hand would be 3 handed.

Besides, even if the circumstances had been different and UTG did not open the past 3 hands in a row and was about to leave I don't see why it's "that" wrong... I've definitely seen and made looser plays before, and I think it's +EV to call preflop considerring I was pretty sure UTG was just finishing his session and the fish called behind. (I might've folded had the fish not called)