how is it possible that a 2000+ fell for this ?

black resigned by allowing checkmate (trying to save the position fails: 5...e5 Qh5+ Ke7 exf4 exf4 Bxf4 gxf4 Qe5+)

@StevenEmily said ^

black resigned by allowing checkmate (trying to save the position fails: 5...e5 Qh5+ Ke7 exf4 exf4 Bxf4 gxf4 Qe5+)

" he blundered checkmate "

thats quite obvious , the question is why did a 2000 fell for this in a classical game

i'm saying black noticed the checkmate but allowed it because the position was so bad, not that he blundered it

if i misread what you meant, then the reason is that piece sacrifices are unintuitive. Also you don't necessarily expect for people to know precisely how to counter your crazy opening with a "trap" of their own. And it isn't really classical if black only took 20 seconds. So the rare miss can happen

@StevenEmily said ^

i'm saying black noticed the checkmate but allowed it because the position was so bad, not that he blundered it

ok i understand now

I've blundered online games like that.
It's similar to how people get scammed. You get hyped up thinking you win a piece (make a good deal) and you become blind for the danger. "If it looks too good to be true, it probably is" , is advice Black should have followed.