The problem is that you only see the national/provincial numbers, and people don't think about how things shift locally.
So take my old riding of Willowdale. The Liberals won that seat with like 55% last time. If you take the provincial swing, the riding basically ends up being 40% PC, 30% each for Liberal and NDP. So yeah, you can say "vote strategically", but you probably have the NDP people thinking the Liberals should vote NDP, and the Liberals thinking the NDP should vote Liberal.
Basically, each side has a reason for their thinking. The overall shifts are not enough to move the riding close to the NDP - basically the riding is not left-wing enough to naturally elect the NDP. But with the Liberal vote cratering everywhere else, they're losing enough there that they can't retain that riding.
And you're going to see similar things in Markham, Richmond Hill, Vaughan, and other areas. Sure, some of those ones will have a strong enough PC vote that it won't make a difference, but there's a decent number of ridings which basically don't have enough left wing support to shift over to that side, where the Liberals have enough to keep 2nd place, but have lost too much to win the ridings. It's just too hard to coordinate 5k-10k people to all en masse move their votes when you don't really know which party is actually going to have the general support.