Xiaomi has published some infographics to amply portray just how successful the Chinese OEM has been over the last few months. The company is now in the top four places globally for smartphone shipments and in the top five for smart TV shipments. Products such as the Mi 10 Ultra and Mi TV LUX have contributed to Xiaomi's outstanding performance.
https://www.notebookcheck.net/Xiaomi-quarterly-infographics-portray-a-company-taking-the-world-by-storm-thanks-to-products-such-as-the-Mi-10-lineup-and-Mi-TV-Master-Series.490057.0.html
So Xiaomi's overtaken one of O or V, I'd say I've been expecting it all along(eventually both O and V, actually) but their market performance till last year has been confusing...