There are three main driving forces.
1. Foreigners are back (on paper 5% in Vancouver but I know people found ways around the 15% tax.   So the actual number is well above 10%. )
2. People are unaware of the OSFI change coming into.  Many mortgage brokers and realtors are misleading consumers by convincing people that "now is the time or never"
3. Quebec Investor immigrant from needs to stop immediately.   At least 10% of investors in Vancouver came through this program.  Free pass to those tourist immigrants.   Many of those went back to their country the moment they obtained citizenship.   A great deal for them, bad deal for Canada.

Lastly, we are already in bubble territory.  I hear that virtually everyone who are buying detached homes are investors. Not a single family bought detached homes in my neighbourhood.   All rent out or sitting empty.  No I am talking about Vancouver or Burnaby. I am talking about Fraser Valley.