The kollel check increase happened less than a year ago. The rent increases started well before that. Housing prices are up significantly so if stands to reason rents are as well. This is happening nationwide not just in Lakewood (although due to supply and demand it is magnified here).
Anytime someone does something good people try to find fault. I have heard so many things (besides my plumbing leak) blamed on the kollel increase.
This is an item that was discussed by the roshei yeshiva and the donors and part of their overall cheshbon. My understanding is that they felt the benefits outweigh the costs.
An important point to realize is that, in the past, a large portion of housing expansion was new development. That typically came with additional basement apartments. At this point, most expansion is happening outside of like and by geographic expansion. This has not come with additional supply of apartments and has tightened the rental market.