Why are the Franks so good?

According to this website the Franks are the best civilization at every skill level. I am having a hard time understanding why that would be the case, yet i don't believe the statistics lie.

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Glossing over the specialties of the Franks didn't help much either.

• Throwing axeman This is kinda like a ranged Champion, but i think i'd rather have a champion most of the time. They also have a bearded axe upgrade that gives +1 range for these units.
• Chivalry: Increases the work rate of Stables by +40% This is a very expensive upgrade that makes me wonder if it wouldn't be cheaper to just build more stables instead.
• Farm upgrades are free: This seems to be effectively a wood bonus, not bad but not that great compared to what other civs get.
• Castles are 25% cheaper. I tend to mostly build many castles if i have a strong unique unit that i want to mass produce, but with the Franks i'd be more inclined towards massing knights, cavaliers and paladins rather than throwing axemen. Castles are quite powerful for defense though.
• Cavalry have +20% HP. This is the big one i think, it means that the Franks have the strongest paladins in the game and therefore arguably the strongest maxed out army any civilization can muster. Yet it also makes them a one-trick pony if they can't do anything else.
• Foragers work 25% faster. This is an awesome early game boost.
• Team bonus, Knights have +2 Line of Sight. By the time you get knights, wouldn't you have scouted most of the map anyway?

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Then we have the tech tree, it seems to be lack luster with no imperial skirmishers, hussars and a weak archer line. Siege and navy is mediocre at best.

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Is my evaluation completely off? Why do the Franks perform so well when their statistics/characteristics don't indicate that they should?