Consider the quotes:
"It is easier for a camel to go through the eye of a needle than for a rich person to enter the kingdom of God."
and
"For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven."
Looking at both of these I would imagine that at around the time Jesus, it was particularly difficlt to get into Heaven. Also, assuming that entrance requirements do not change that much over time, all preceding applicants to Heaven must have also found it equally difficult. Now consider this. Jesus gives his life on the crossn forgiving everyone's sins and so paving the way for all people to enter Heaven. The previous rate was probably something equivalent to one of every 100,000 souls due to the high moral standards required. So the rate at the time of Jesus' death likely increased something on the order of 100,000 times. Even in an infinite space, this is quite an increase. We are also forced to assume that there is either only one entrance to Heaven or more than one Saint Peter. Since there is only one Saint Peter, it would seem that there are now 100,000 times as many people he must interview. However, the entrance rerquirements being negligible, he can allow most of then to pass without much more as a "Welcome to Heaven! Here is a map of Heaven and also a brochure mentioning some of the best places to shop and dine. And remember, they don't call it Heaven for nothing!".
Also, in addition to this new influx, all the souls in limbo that didn't make the original cut into Heaven, enter Heaven at the moment of Jesus' death. Considering the sheer number of people that didn't make it into Heaven before and the fact that humans have been intelligent/ possessed souls for well over 10,000 years, there is also likely almost 100 billion souls wanting enter Heaven all at once.
Still remembering that entrance time in negligible, the population of Heaven must have grown enormousely at the time of Jesus' death. This can be roughly compared to normal immigration. Still using previous values, there is approximately 100,000 times as many people immigrating to Heaven as there are already in heaven. This would likely cause enormous civil disorder and widespread unemployment all over Heaven. Th ensuing mass riots regarding broken promises consisting of billions of people would likely cause massive damage to the infrastructure of Heaven. These riots and cries for help would envariably ensue until God took some kind of affirmative action. People have now come to Heaven from limbo, now away from their families, jobs, affordable homes, and dogs, and are now forced to leave on the street or in cheap housing with no money to their name (Since Heaven should be infinitely better than limbo, it is likely that its economy is also infinitely better, thus making the limbo dollar completely worthless). And the influx of people would still continue at the new large rate.
Assuming that God is all-powerful, it is likely that he considered all possible solutions, and in three days he found the best one. Sending Jesus back. God realised his mistake in redeeming all sins so thought that maybe if Jesus went back the souls would too and he could get back to watching CSI:Miami (It's not that great but it makes you think). On discovering that this didn't work, God was forced to take his son back and began to fight off the riots by constructing more livable space in Heaven. It is likely that during this time of massive restructuring, individuals producing detour signs made a large fortune in the poverty stricken Kingdom of Heaven. Considering that it took God seven days to fully create the Earth and all people are promised their own perfect world, he would have to create at least 100 billion worlds and increase his rate of production by 100,000 times. Working at his normal rate this would take God approximately 2 billion years to simply meet the demand of those living in limbo. Just taking that into consideration and assuming that he halted entrance to Heaven as soon so the problems arose, God would either need to increase his production rate by a million times or increaes occupancy by a million for Heaven to be now as it was promised. This of course not taking into consideration the backlog of people now in limbo from when he shut off the gate. As it is unlikely that the immensely disatisfied immigrants would take a million times less than they were promised, Heaven is either still under construction or consists almost entirely of very poorly built structures (assuming a rate increase of a million would produce structures one millionth the quality). Also, anyone dying now would be forced to wait in limbo until heaven's capacity has inccreased to allow the new population. So just a tip to everyone, stay alive as long as you can. Cheers