Next time you are offered a trade, the scambot will instantly decline (or counter) the offer and create a new trade of its own — from another Steam account. These bot accounts usually look exactly the same as the ones you were supposed to trade with. Without any suspicions, you accept the trade and give your item away to a scammer.
This is strange — why would a scam bot just wait for me to accept a fabricated trade and not steal my items instantly by itself?
Because Steam implemented 2FA verifications for ALL trades (they need to be confirmed via the Steam Guard mobile app). Therefore, even having your credentials, the bot would just sit and wait — sometimes for weeks or months till the moment you are offered a trade. Once it happens, you are much more likely to fall for the plot and approve the trade via 2FA.