The answer is that it is all because of their own stubbornness combined with problems with their good friends, the Egyptians.
There have been big clashes in the Sinai between the Bedouin and the Egyptian security forces - today some 18 policemen were kidnapped. The disagreements are over the smuggling of goods (and people) to Israel and Gaza. Egypt is trying to curb illegal smuggling and sometimes they kill the smugglers.
Meanwhile, as I've reported, northern Egypt is suffering its own fuel crisis - mostly for butane used by consumers and especially the cylinders they are stored in. Residents are rioting and upset. So Egyptian security is cracking down on smuggling to Gaza, and it looks like their efforts are affecting the power plant fuel as well.
Because, believe it or not, when Hamas decided they don't need fuel from Israel any more, they were not relying on a steady supply of diesel from Egypt being sent in trucks through Rafah - but illegally smuggled diesel going through makeshift pipes underground!
Putting all this together, Hamas has created this crisis because of its hate for Israel - a country more than willing to supply Gaza with fuel at market rates.
Meanwhile, Egypt's ambassador to the PA says that Egypt will do what it can to ease the crisis - but it will not tolerate smuggling. Egypt's plan, as I have previously reported, is to hook Gaza up to its own power grid. That will take some time. Meanwhile, there is no easy way to get fuel to Gaza - except through Israel.
(h/t G)