They could always do that from day one. They could flood the network with small, useless transactions that they over-pay for in terms of fees, just to drive fees up.

They’d have to keep printing money to do it. They would draw attention to bitcoin via the Streisand Effect.

Bitcoin miners would make an absolute killing. Layer-2 development and adoption would likely accelerate (it already did a bit this last week). The network would suck for small transactions for a while.