Well I had the same question has you, but after thinking about it I came to this conclusion:
The Templars did not know about the incoming tragedy.
So why do they not care at all that a world-changing event is about to
destroy what they care about most - order?
We can't say for sure that they didn't try, because the satellite was probably their idea to prevent the tragedy.
The Templars set about gathering the remaining Pieces to ensure
"absolute peace", although they soon found themselves in a race
against the Assassin Order to obtain the Pieces first.
They planned to send a satellite with a Piece mounted on it into
orbit, with the launch scheduled on 21 December 2012. Ultimately,
Abstergo cancelled the launch of the satellite as they were unable to
obtain the required Piece of Eden in time.
So maybe this was their try to save the planet. Even the Minerva says that they wasted away their time (to save the planet) fighting each other (Assassins vs Templars).
"I had hoped you might find this place – and finish our work. But it
is too late. You and the Templars have squabbled over our refuse. You
have wasted centuries. And so you have lost your chance. You cannot
hope to stop the end now, Desmond. Only to survive it."
―Minerva, to Desmond Miles.
But the satellite was an Abstergo Project called Eye-Abstergo.
This satellite was planned to ensure that a New World Order would be
enforced on Earth with the Piece of Eden's powers.
"If we were to place just one Piece of Eden within a satellite and
angle it toward the Earth... well, utopia would be within our grasp."
Upon entering low Earth orbit, the Eye would amplify the Apple of
Eden's power, as well as boost Abstergo's observational capabilities,
and locate "individuals with potential."
Though highly uncertain, preliminary analysis suggested that the
satellite would allow the harvesting of raw data, and would "awaken in
humans what should have been ours from the moment of our creation."
But it doesn't make sense since Abstergo planned to launch it December 21, 2012
So honestly, my answer is: The Templars did not know about the incoming tragedy.
Their plans just don't add up and Ubisoft isn't stupid not to notice that big of a plot hole.
The Templars interpretation of Minervas Speech must have been off.