We don't have all the details yet, but apparently not only was the retreat of Severodonetsk a well laid out trap that was legitimate, but it was so complete Russia may lose everyone that went into the city initially and are completely decimated. They are now down to a small pocket fighting for their lives with no reserves available to relieve them.
That doesn't mean that Russia cannot retake the city, but what we do know is that Russia went from 80% captured to 80% liberated, and the blow dealt was extreme.
https://twitter.com/user/status/1533522639398092802
This cannot be overstated, the Russian major offensive, their push with the majority of their troops that they abandoned the Kyiv and Kharkiv front for, has just had its main army obliterated and remnants hemmed in.
Avoid mainstream media for information, they sensationalize on purpose, are usually days behind on correct information and focus on outrage (Russia doesn't care)
“Appear weak when you are strong, and strong when you are weak.”
If your enemy is secure at all points, be prepared for him. If he is in superior strength, evade him. If your opponent is temperamental, seek to irritate him. Pretend to be weak, that he may grow arrogant. If he is taking his ease, give him no rest. If his forces are united, separate them. If sovereign and subject are in accord, put division between them. Attack him where he is unprepared, appear where you are not expected.
― Sun Tzu, The Art of War
Putin played right into the oldest war trick in the book.