Those are specifically alive countries at the end of the set. Dead ones aren't counted in the total.

Large scale wars almost always cause a major influx in membership due to warring tags recruiting old buddies back to the game, in addition to the current netting meta being very boring FFO only. You can play solo and win the game netting, but wars require members, so there's more motivation to recruit. The 10 largest membership sets of the last decade were all server wars, with those involving attcks on LaF generating the most.