With the way that the ATP has redesigned their rankings system, we will continue to see this back and forth occurring. The points system as it now currently stands over-rewards the challenger system like crazy (this coming from a huge challenger supporter), and it is just ridiculous. For example, a challenger win is either equal to or exceeds the points given to a semifinalist at a 250 event or a round of 32 at a best of five set Grand Slam, which is just crazy. So whoever wins next week's Leon challenger with a current 359 ranking cutoff and where the highest ranked player entering is 136 will get more points than a semifinalist in Dubai or Queens or a player that wins two matches at Roland Garros. Thus we will continue to see unknowns crack into these 65-120 positions, and then eventually slide back down after a bunch of main tour losses to be replaced by other players who had to pick up easy challenger points.
It's insane, and the ATP really needs to go back to not excessively weighting challenger results...
That is a very great point and I totally agree, players should have to earn their places in the top 100 well and truly.