His success would have been greater if he got his name out there. Be in the community and meet people so that they can support your work. I don't think it's all to blame on that, but he could use the help of others and their support to excel and succeed.
Yes, Perelman's lack of success in mathematics is because he didn't tout his success in the subject. Half of being successful is tooting your own horn and convincing other people that you're successful. Just ask any politician. Perelman should have spent some of his time convincing others that he was a brilliant mathematician.
I believe that Grigori Perelman's self-described lack of success be attributed to his extremely high bar he set for himself. By most traditional definitions of the word, Grigori Perelman should be considered a smashing success. He was awarded, although declined, the highest honor in mathematics and its accompanying 1 million dollar prize. The self-described lack of success was not accomplishing his personal goals that perhaps were not achievable in the first place.
Grigori Perelman was responsible for huge achievements in the field of mathematics. Although he withdraw from high-level mathematics I do not feel that any perceived lack of success can be put down to his lack of participation in the community, in some instances such isolation has led to ground-breaking discoveries.