This is because in a bid to entice players to return to the game and to stay home, Blizzard has implemented the Winds of Wisdom. This basically gives all players a 100% experience buff which means that all experience they get in the game, like killing monsters and completing quests, will be essentially doubled.
According to Blizzard, “If you’re staying inside and find yourself returning to Azeroth, or if you’re leveling another character (or two), you’ll be getting a special bonus to help you on your way. Beginning today through April 20, 2020 all players in Battle for Azeroth will gain an experience buff called “Winds of Wisdom” which will increase experience gains by 100%! (This includes Starter Edition and Legion players as well.)”
If you’ve already maxed out your current character, now’s actually a pretty good time to start leveling some alts. Blizzard also mentions that this experience boost will stack with Heirloom items (which already grant XP bonuses), meaning that for some players, they will be able to get more than double their XP.