Since you insisted on using a website, I'll quote from there, as well.
3.5-6 years? Are you kidding. It says right there that the AVERAGE was 5-6 years, and that 3.5 was the low (meaning very rare... high would probably be about 8 years, averaging out to 5-6 years, which matches up with the figure of six years that I gave). They didn't include in there that SUCCESSFUL mating (meaning a litter results) doesn't usually happen until 8-10 years of age, usually closer to the latter.
Three females to one male... It's an averaged statistic taken straight from a 294-page published document (by a Doctor of Wildlife Biology) that I had to read during my training. If you want a reason, it partially has to do with the fact that a mother keeps her cub with her for so long. Only about 1/3 or less of sexually mature females reproduce every year for various reasons (usually having to do with the afore-mentioned reason). So say there are 30 females and 30 males in a population. If only 1/3 of the females are going to be mating that year, that makes 10. 10:30 = 1:3. Get it? Ever watch the Discovery Channel? Remember when you see the males of almost any species fighting over a female? There you go.
The site you gave also stated that a female cub is born approximately every four years per sexually mature female, further backing what I stated.
You took the extreme statistics from that site and then tweaked them to your liking or misinterpreted them, altogether. You also forgot to factor in a number of things.
Yes, the population did increase, which is why it made the front page of the news. Do you think that if that was a normal thing (which is what you're arguing), it would make front-page news? Hell no! I'd bet money that conservation efforts played the major role in the extreme population increase, as JD already stated. I'm not sure you really understand the concept of exponential growth...