Chronological order....
Hamas was founded as an off-shoot of the Muslim Brotherhood.
Hamas was officially chartered to establish an Islamic state in the area of Israel. Not just Gaza and the West Bank, but Israel. Meaning their openly overt intention is the destruction and removal of Israel as a nation.
Hamas deposes Fatah from Gaza.
Hamas takes power from the Palestinian Authority.
Egypt declares Hamas an enemy after ousting the Muslim Brotherhood, and closes tunnels.
Rocket attacks from Gaza increase throughout May.
As the rockets increase, Israel clamps down on Gaza. Hamas forms a unity government with Fatah on June 2nd.
Fatah still has no real control over Gaza, but proclaims recognizing Israel, and a rejection of violence. Israel agrees but requires that Fatah reject Hamas violence.
June 15th, three Israeli, un-armed, non-soldiers are kidnapped and murdered, while Gaza people celebrate, have a festival in the streets, and post pictures of three blood red fingers on social media.
Fatah is at odds with Hamas. The Palestinian Authority fights against Hamas, and helps IDF to locate and destroy Hamas tunnels.
As a result, Hamas uses the tunnels to lunch 100s of rockets into Israel, in the largest wide area attack in years.
Israel starts their ground war offensive into Gaza, backed by PA and Egypt. Fatah, though not directly endorsing the action, is very much against Hamas and Gaza.
The unity government of Hamas and Fatah, was doomed at the start. Fatah was, and is, open to finding a peaceful solution, of a mixed Arab Israeli government in the land of Israel.
Hamas was never willing to accept that, and is chartered, and hell bent, on the absolute elimination of Israel as a country.
There is no possible way for those two goals to unify.
Anyone who thinks otherwise, is on the far side of insanity.