As I understand it, your original flight was cancelled (for unspecified reasons). You were informed less than seven days prior and were not put on a replacement flight that departed no earlier than 1 hour before the original departure time and enabling you to arrive no later than 2 hours after the original arrival time. This is why you are entitled to compensation.

The further travails of your replacement flight, and whether or not a strike is responsible for delaying that replacement flight, are not relevant.