The Fantasy Variation is one of the best opening choices for club play. With it, White accepts possibilities of Black equalizing in exchange for the chance to demolish Black's defenses. White intends to maintain his pawn center and quickly develop. After 3... dxe4, White must avoid recapturing fxe4, as this leads to a quick loss after 4... Qh4+. Instead, 4. Bc4! is an aggressive option that can quickly send Black to floundering, focusing on f7 as a target for attack. Black's best chances are in keeping the position closed with 3... e6 or 3... g6, but this leads to equality and nothing more, and only if played correctly.
How on earth white is "developing quickly" following 3.f3?
Isn't 4...Qh4+ a slightly illegal move after 4.fe4?
Factly, Black's easiest plan to equality is 3...fe4 4.fe4 e5 (see the analogous video by GM Sam Shankland on this site).
Following your suggested 4.Bc4 white already has to fight for equality after 4...e5.
Perhaps the best chance for Black to equalize is to keep the position closed with 3... e6 or 3... g6, as the White player is often looking specifically for an open position. The move 3... e5 is Black's most aggressive choice, as it keeps the position open, but allows attacking chances for White.