I think their hand was forced once the overwhelming number of reservations become evident in the first week. They probably would have preferred to stick with their original plan as well. People went in expecting a 2, maybe 3, year wait and were resigned to that and planned accordingly (finances, interim car if necessary, etc.). However, by the end of the first day, even those who had pre-ordered that very day were at risk of having their deliveries push out beyond that. By week 1, the situation had become untenable. A 2-3 year wait is looking more like 5+, so would people be willing to wait that much longer? And the situation gets worse with every passing day. Should they just shut down accepting any new reservations until production ramp-up? None of this would be well-received by the public or the stock market. The Model 3 may be the hottest car on the planet right now, but would that remain the case 4-5 years from when they finally hit their stride and start making a dent in the backlog? The only choice, given the circumstances, is to bring the schedule forward and to announce it. Ramping up in secret won't provide any comfort to anyone still thinking of buying a Model 3 (remember that Reveal 2 is anticipated generate another wave of pre-orders). These people may simply look at the backlog of existing reservations and Tesla's original roll-out schedule and say "screw it, why bother". With the accelerated schedule announced, Elon was able to tweet that you'd better get your reservation in soon if you want the car by 2018 (i.e., you can still get it in a reasonable timeframe even if you order now)... and that anyone who ordered during the pre-reveal has a good chance of getting a car in 2017.