As much as I have contempt for Regency about leaving yet another empty lot or pit in the middle of downtown where a perfectly fine building once stood, this particular project was hit with a ton of bad luck.
The demolition and pre-construction all occurred before the Valley Line started construction at 102nd ave, they were given the option to either demolish the building and then wait for the VL to finish to start construction, or to wait to do both. They opted to demolish the BMO Building before, showing that at this point they were committed to this project. Then the VL was delayed several years, and then what was probably the nail in the coffin for Tower 101 was COVID.
I still question why they didn't return to this project, surely they aren't going to make back anything (in fact they will most likely lose a lot) from selling this empty lot. Even if the land is more valuable than what the BMO building was when it was demolished (which I highly doubt in Edmonton). It seems like very poor asset management to me, though I am no developer.