Because less than 100 years ago what is now Israel was Palestine.
For much of the last thousand years the vast majority of those living in the area were Muslim.
The mid to late 19c saw a sea change of religious, cultural and racial nationalism and fundamentalism. From Crimea, to the Levant, to Ireland, to trades unions, socialism, communism, Zionism etc. From 1914 onward imperialism and colonialism were in their death throws. The Ottoman Empire had collapsed, in Russia the Bolshevik Revolution, the collapse of the Habsburg empire. Nations were redefining themselves from dynastic to democratic or autocratic entities.
From 1917 to 1947/8 Palestine came under British control and in 1920 the British Mandate, in 1922 Muslims were vast majority of Palestinians. Armed factions of both Jews and Muslims fought both each other and the Brits. Up to 700 Palestinian villages were razed by the British. As the Nazi threat increased the British allowed only a very limited migration from the Jewish diaspora to Palestine (despite indications of the Holocaust to come).
In the eyes of the west the horrors of the Holocaust and the post war aggression of the USSR legitimized Zionist calls for a Jewish homeland. Europe and the UK had lost the appetite and the ability to maintain expensive and unpopular overseas expeditions. The star of the US had risen as world's new super power.
In 1948 the State of Israel was formed by the UN despite Muslims having a 2:1 majority. Europe and the Brits were happy to wash their hands of it all, and the US would do anything to win votes at home.
The State of Israel was imposed on the indigenous Palestinian population.
Palestinians were and are still understandably upset. Since that time Muslims have been persecuted, their property and possessions seized. The have been expelled from a land they had lived in for almost a thousand years. Some estimates are that for every Israeli casualty there have been ten Palestinian.
Does this excuse the obscene 7/10 massacre - absolutely not in one little bit.
Does the Holocaust excuse the ethnic cleansing of Palestinians and the colonisation of what is now Israel. Absolutely not.
Hamas have a stated aim to destroy Israel.
The governing Lekud party in Israel claim settlement of land (of their choosing) as an unassailable right.
(And don't forget Hamas is backed by Iran, who are allies of Putin, who has invaded Ukraine (see late 19c comment above) who is allied to North Korea and supported by China who are trying to expand into the Pacific and consider Taiwan as their own.)
Or, to put it simply: it's a shit show in which the suffering will get worse before it gets better.