There are two factors in play here as far as I can see:
a) more players on the ladder as a whole know how to pick and play decently. the level of overall competition rose (no big surprise with so many players participating in the 1v1 ladder these days). you see former no. 1 players ranked in the 20s and 30s.
b) top players that have been out of the ladder for a long time seem to have their biggest problems at the start of their run nowadays - and usually stabilize thereafter (if they don't leave after their first losses). as i see it, without the immediate ladder experience they have to shake some rust off.