Black is up the equivalent of a pawn & controls more squares/space BUT, & this is the most important thing in the position, just look how far ahead black is in having ALL their pieces out & fighting while white is not only still stuck on the starting spots but it'll take many more moves to develop whereas blacks pieces whole army is almost out. Look at development this way, if ur in a group fight & ur by urself & 3 people r attacking u, wouldn't u want a few people to hurry up & jump in to help u? Hurry & get those pieces out & into the fight.
why is this position completely lost for white?
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So looking at the post two before mine, it looks like you're using a depth of 38. Many positions which are completely won will give high evaluations if you calculate that far. A rough interpretation is that black can win another 3 points of material after the next 20 moves and a further 4 points of material in the following 18 moves. Humans can't see that far ahead. You'd need to play it out to find out where that material comes from. Black has 3 minor pieces and the Queen activated, a Rook 1 move from activation, the other Rook 3 moves from activation plus a Pawn in the centre. Whereas White has all of their pieces on their starting squares. That should be enough for a human to see that the match is won for Black provided they don't make mistakes. I'd start by pointing those Bishops at the King's side but there are undoubtedly a multitude of lines which realise the win.