How do gambits help in rapid development?

Hello everyone,

         this is my very first blog post on chess.com and to start with I have chosen a topic that has been puzzling me recently-gambits.A frequently used phrase to describe gambits is "giving up a pawn for rapid development".But what I don't understand is-how?How do gambits help in gaining development?              Let us take the Queen's gambit,for instance.This is of course the opening in which it is considered wise for black to reject the offered pawn.But even from white's perspective,the move 2.c4 does not open any lines for his light-squared bishop.Indeed,in QGD this move all but closes the f1-a6 diagonal for white's light bishop.i know that the term "furthering development" doesn't imply immediate development,but even if white gets some queenside space as compensation,black can immediately start an onslaught on the kingside.So where's the lead in development?

        Even in KGA,after 2...exf4,black can follow it up by 3...Qh4+,putting white's kingside under pressure immediately.I know that the whole point of the king's gambit is to open up the f-file for white's KR after castling,so as to launch a direct attack on black's weak KBP at f7(by sacrificng his own KBP-how ironic!).But as I metioned,black can refute this threat from white.Besides,after 1.e4 e5,if white plays 2.d4 instead of the king's gambit,it opens lines for both of his bishops while also givng him the option of winning his pawn back(if 2...exd4,3.Qxd4),although this can lead to a loss of tempo for white as black can reply with ...Nc6,driving the queen away.I think the Danish gambit was a strong opening as it gave white a solid combination with both his bishops controlling vital squares,but over the years it became easily defendable and now it is outdated.

        So why,despite all these glitches that I mentioned,are gambits so popular and how do they enhance development?Please leave your comments,guys and let me know what you think!