I mean game was pretty much over by the time Leverkusen got their red card, so acting as if they did something magical after they were left with 10 players isn't really a good statement, surely a good clickbait headline but the reality is that they were 3-0 ahead before that red card, and they just got a good defense going afterwards, that's it. They could have won with even more difference that much is true, but that doesn't mean that we are going to end up with that much of a trouble to begin with.
Leverkusen nearly lost this season too early by their terrible beginning but now after two thirds of season, they have came back as a runner up and are still competing for the title with Bayern Munich. This rise shows their strength and this latest hard win with only 10 players, proved that Leverkusen are actually strong, from past season to this one.
6 points is a small difference for Leverkusen and this club only needs to win 2 matches if Leverkusen continues to perform consistently winning and Bayern loses points in their 2 matches then Leverkusen can overtake them, but so far Bayern Munich is still performing well and has not shown any signs of decline, yes even though Bayern Munich almost got a draw when playing against Hostein Keil but that did not happen because Bayern Munich had ensured their victory by scoring many goals before the opposing club replied with 2 goals which became 3 goals in the last minutes.
6 points in difference are not small in general and in particular when Bundesliga has only 14 more matches. Leverkusen needs Bayern Munich to lose 6 points in last 14 matches, that can be 2 defeats or 3 draws, but Leverkusen with worse goal difference even need Bayern Munich lose more than 6 points.
It can be considered as not too big difference, not too big difference is different than too small, if the leader is not Bayern Munich, but this club dominate Bundesliga historically and this season too. Expect them losing 6 points in last 14 matches is quite hard condition for Bayer Leverkusen. It has to take into consideration that if Leverkusen lose more points, their race with Bayern Munich will become harder.