I suspect this is primarily because the tax for leasing an EV is going to double by January (from 4% to 8%, vs 22% for ICEs, but still, double). So people whose work perks includes a lease car and who have been considering electrical, are all getting one quickly now. And the Model 3 is one of the better EVs on the market, so there you go.
Model 3 sales in NL will drop tremendously in 2020.