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Wow- sorry to hear of your troubles...given that the flight to DEL was delayed until 22:00, I am surprised they did not get you on the flight . One reason I can think of is that the flight was oversold and your seat was already given away..>Do you have the AC app that shows you the Standby and Upgrade list?
Having said the above, I would not have booked on a flight from YUL that allows only a 1hr 1min connection time at YYZ- especially not in the winter. I understand that may be a legal connection, but lots of crap happens in Winter. I would have booked the 18:00 YUL-YYZ (which arrived pretty much on time that day) to give yourself a bit of buffer.
Lastly, at that point where they denied me boarding, I would have insisted that they send me through Europe (FRA, LHR or perhaps IST) to arrive in DEL early the next morning from when you should have arrived...there are many viable options from YYZ...
Happy flying!