Since southpaw Ibragimov beat Holyfield in October 2007, only 3 fighters have won heavyweight title fights while weighing less than 225 lbs: Haye, Wilder and southpaw Usyk. Since October 2007, 14 fighters have won heavyweight title fights. The dominance of the Klitschko brothers had a lot to do with the relative absence of sub-225 lbs heavyweight title winners from 2008-2014 and must have deterred a number of top cruisers from moving up. Haye was not deterred but was dominated by Wlad, while Wilder and Usyk never fought a Klitschko. Haye and Wilder beat weak-mediocre champions for a title (Valuev away, Stiverne home) while Usyk beat a strong champion (Joshua away) but none have beaten the consensus No.1 heavyweight champion. All 3 of the sub-225 lbs heavyweight title fight winners since October 2007 were very fast, 2/3 had massive power and the other was a highly skilled southpaw. The minimum heights were listed as 6'3 (probably 6'2 in reality) with 78 inch reach and the minimum weight was 217 lbs (when winning a title).
It's difficult to win a HW title unless you are ****ing massive. Look at the 3 non super HWs to win a recent HW strap. Haye, an ATG Cruiser and serious banger. Wilder, vicious power and 6'7". Usyk, arguably GOAT Cruiser and a slick moving southpaw.