There are three kinds of lies: Lies, Damned Lies, and Statistics. Not saying that these stats shows not correct information or something. But it doesn't reflects real situation fully.
Same report also classified Ukraine to Upper middle income from being Lower middle income. Also, their GDP had increased. How such thing can in country which is at war for 2.5 years, their economics can't work even at half potential and when they lost few millions from their population?
Russia, your quote already says main reason why it happened - their military industry is working at almost full potential, not like during peacetime.
Your question already contains the answer. The massive outflow of the population from Ukraine allowed it to rise to a place in the World Bank's ranking table based on a metric that is calculated per capita.