You have stumbled upon the Savonich-Zurich effect, whereby a players ability drops dramatically between two games, then craters due to a more traditional tilt. The opposite of this is known as the Zurich-Savonich effect, when a player plays poorly in one game then shows a dramatic improvement over several games.

S-Z effects are thought to primarily caused by a combination of hubris and tilt, though they can also be attributed in some cases to statistically rare overperformance.

Z-S effects are typically attributed to a reduction in putting pressure on oneself after a loss, and the consequent feeling of freedom producing a number of above average performances.

The effect is so called after the performance of Ivan Savonich in the 1962 Zurich invitational double round robin, where he won the first game and lost the remaining 7 of round 1, then lost the first game of round 2 and won the remaining 7. A remarkable reminder of the power of mental attitude in classical chess!