FWIW - almost all wildfires in Canada start with lightning. It happens often in Western Canada just as wildfires are more common in the Western US.
These fires start in very remote areas. People have little concept of how remote much of the forests in Canada really are.... we are talking about massive swaths of forest and tundra with no road network.
Canada has a different approach to fighting these because of how remote they are and a lack of resources. They generally try to protect private property and infrastructure and let the fires burn and its probably a correct approach for better forest management because the more fires you suppress he heavier and larger the fuel loading is for the next one.
Another thing that I believe is influencing this is the pine beetle. It has swept through Western forests in the US, BC, and Alberta and I understand it is present in central and eastern Canada now. When you kill off lots of trees in overgrown forests it acts as a ladder fuel and puts fire up in the trees when it might otherwise stay mostly on the ground.
Just my .02 and I don’t view this as a conspiracy or terrorism. There are certainly wildland arsons but most are accidental either from natural causes (lightning), trains (I have seen a few of these), and/or negligence (discarded cigarettes, slash piles, machinery) there is proof positive for lightning strike fires and presumptive starts along rail lines.
When vegetation dries out (uncommon in the humidity on the east coast) you can start a fire simply by your lawnmower hitting a rock (this happened to me a few years ago on riding mower along my driveway).
To be more precise - the largest and biggest wildfires there start with dry lightning. Numerically I think they are around 50% of starts by lightning but those lightning fires are responsible for more than 80% of the land burned.
I have not looked at their stats recently but that is what they were a few years ago.
Also, widespread organized arson in remote areas would be very hard to keep secret. But conspiracy theories are so much fun.