Yes but STCUM (now STM) responded accordingly by running 3-car trains every 10-12 minutes and closing the line as early as 11h15pm.
I don't recall ever seeing 3-car trains. I only saw 6-car trains, even in the 1980s. Have you seen 3-car trains? I didn't ride it that often, living near the Orange line.
Took time but the blue line has good ridership with more frequent service, 6 car trains and closes as late as the other lines.
I thought they were 9-car trains like the other lines - to tell the truth, I haven't ridden it in years though - only ridden the Green and Orange lines recently. Ridership is still low enough that they run 6-car trains?
It's an essential part of the network and gives alternatives to riders when there are problems on one of the branch of the orange line. With your logic, it should have never been built because the projected ridership would not have matched the green and orange lines.
If you take the politics out of it, the Sheppard Line and the blue line are almost virtually identical in term of locations on a similar network, and both lines started with low ridership. Today, the blue line shows that Montreal was right to built it and what the Sheppard line could have been if it was built as envisioned from the get go.
If you take politics out of it, the Blue line is build through a dense residential area - probably denser than the Danforth. The Sheppard line goes through suburbia - and not only suburbia, but suburbia with quite big yards. There's a bit of density right along Sheppard - but not enough.
It you take politics out of it, the Sheppard ridership projects for the full subway - don't support full subway ANYWHERE on the route, with a peak ridership well below 10,000 at Yonge - let alone at the outer edges at STC and Sheppard West station, where it becomes embarrassing even compared to the current ridership.
And yes, it was envisioned to stop at Don Mills. That was being discussed even during the Peterson government. There was never any timeframe put to the next phase.
Your claim that Blue line in Montreal was built in phases is just wrong. The Orange extension from Bonaventure to Cote-Vertu was done in stages.