Perhaps the invited "guest tops" were shady stating their sex-act preference. Perhaps the photo wasn't the best representation of the bottom. Perhaps the bottom had personality or intimacy quirks that don't bother you, but turned off some of the guests. Perhaps half of the guests are just selfish pricks (with selfish pricks attached), who always intended just to play with the most attractive guys. Perhaps some of the guests had partied a little, or a lot, beforehand, and lost their impulse control, or ability to get hard.
Perhaps… a thousand possible reasons in varying combinations.
Perhaps, as well, there's a challenge in the structure of the hoped-for gang bamg. To bring seven or eight guys together, for a pre-ordained plan to please one bottom -- well, it leaves a lot of spare time for all these drivers while they're waiting for the tunnel to re-open. When you see this type of hour-long, single-bottom adulation in porn, that's because it's porn. Judge me as you like, but if I've just tagged-out after my three minutes with bottom boy, I'm not going to spend the next half-hour pinching his nips or reading The Economist to conserve my energy.
In the end (padon that pun), perhaps these gang-bang guests were simply being themselves, for better or worse, on that given day.