I'd been playing since 2013 and the top 2 powers were Zachary Hudson and Arissa Duval. I left the game in 2016 to try other games and only came back 2 weeks ago to find Edmund Mahon as the top dog.
Is he a newly introduced power or something?
Mahon's been around since the beginning. The only new power since Powerplay was introduced is Yuri Grom. Depending on when in 2016 you left, you probably just missed Mahon getting to the top.
It's not really about the bonuses they give (Aisling Duval's prismatic shields consistently attract far more supporters in numeric terms, and the Federation has a greater number of dedicated pilots) but about other factors. Mahon's bonus is okay but not all that good compared with some others (Mahon: +20% trade ... Li Yong Rui: +200% exploration and 15% outfitting discount, Lavigny Duval: +100% bounties) and his equipment item is the worst of the lot.
1) There's one Alliance power and four Imperial ones / two Federal ones, so Alliance loyalists don't have to divide their efforts
2) The Federal powers are crushed in the middle of everyone in high-value systems, so everyone fights them.
3) Alliance space is in a fairly clear area at the top of the bubble which mostly isn't of value to anyone else (it's either too far away from their HQ, or they're too busy defending what they've got) ... but this also means Mahon hasn't made that many enemies either.
4) In the early days of Powerplay there was plenty of spare space to expand to, so power size and standing was strongly connected to their initial size (where Hudson and Lavigny-Duval were the biggest). Now all the spare space has long been used up, so power size is much more determined by other factors.
5) With very large powers Powerplay is basically an optimisation problem, and the Alliance are good with spreadsheets. Having a poor weapon is actually an advantage because they don't get as many people grinding merits in highly sub-optimal locations just to get prismatics/packhounds/etc, and messing up their plans.
