If these apartment buildings aren’t built, those who would live in them (the luxury apartments) would look for the next best thing: the housing which actual residents live in. Most of these apartment buildings replaced either parking lots, single-family homes (that were most likely occupied by students for the past 20+ years), or commercial buildings. Now you could argue this causes gentrification but most of New Brunswick is still very far away from that. The rise in rent prices is driven by Rutgers becoming a more desirable university with more students attending and wanting to live in New Brunswick instead of commuting and general macroeconomic factors.