>would you kindly elaborate on the reasons behind the rejection. Thanks
No. Not ever in this forum, check out the TOS for why.
I will address the "seemingly" part. Since a site suggestion doesn't force anyone to do anything in any particular time frame, you should not assume that anyone has done anything in any particular time frame.
You've suggested the site.
If a site IS rejected, the reason would be because (1) the webmaster had been REALLY abusive, or threatened serious abuse (and where that applies, which isn't often, the only rational solution would be to avoid further contact at all costs, right?) , or (2) because the site didn't seem to contain unique content (and the webmaster always knows the uniqueness of his content better than the editor can, so there's nothing we can tell you that you don't know already.)
The third possibility, that the editor made a mistake, can best be handled by waiting a time (I'd suggest six months) and resubmitting. Once. That will get a re-review WITHOUT providing an opening for the webmasters with abusive tendencies (which, unfortunately, we can't tell from the others. And true, the vast majority of webmasters don't get physically abusive, but ... fact is, the vast majority of rejected sites aren't errors either. Bitter experience says entering discussions about rejected sites is much more likely to find abusive webmasters than editing mistakes.)