We already know how to prevent more extinctions. Better environmental laws, more green spaces, better conservation efforts, less suburban sprawl, etc. You know, things that will never happen.

IIRC, the primary reason we're even going with this route is that one of the primary things stabilizing the arctic permafrost was actually the presence of snow-wading megafauna changing the rate of heat dissipation in high-wind tundras. So, they're trying to bring the wooly mammoth back to try to keep more permafrost around.

ETA: Here's the company actually saying this is the primary reason for doing it. Its about restoring the biodiversity loss from humans being an all-around virus for the last 10000 years.

We have to experiment with mice before achieving the ultimate goal of laser shooting sharks.