>>55249040Ground AND Fighting resistances are both huge defensive boons, and Flying being treated like Bug (loads of Pokemon, few strong ones) means that Bug is often the more prominent of the two. That also helps Bug since that makes one of its weaknesses an uncommon attacking type while Flying is also weak to Ice and Electric.
A lot of weaker Bug types could actually be pretty viable with a stat buff. Forretress has 465 BST, but with a +50 BST buff it would be meta relevant again. Galvantula was already meta relevant before it got outclassed by Ribombee, but even a buff from 472 BST to 492 (assuming +10 to SpA and Speed) would make it a monster. A small +10 Speed boost to Heracross would make it viable again too. Crustle, Escavalier, Durant, and Armaldo are all also salvageable Pokemon.