They weren't donated to Israel, they were purchased at no small expense from Czechoslovakia.

The Czechoslovak weapons industry has a long history, and their facilities were used extensively by Nazi occupiers and their allies/collaborators to produce weapons, tanks, and aircraft. Many of these facilities used slave labor. This caused problems for everyone using those items, since the people enslaved the by the Nazis often sabotaged weapons where and when they could. Many Israeli soldiers were Holocaust survivors, some had been enslaved themselves. After WW2 there was a lot of devastation, the USSR also confiscated significant amounts of industrial equipment and machinery. So, to bolster their economy and arms industry the Czechoslovakian communists decided to sell their surplus to Israel. The money would help them rebuild so they could retain some independence in the arms industry, which they did. The Czechoslovakians built more of their own designs than any other Eastern Bloc satellite state throughout the Cold War. The money they made selling weapons to Israel was obviously far from solely responsible for this, but it definitely helped.

There wasn't an ideological component, being a Zionist was enough to get you imprisoned in the USSR, if not shot (under Stalin least). In Czechoslovakia German speaking Jews, including many Holocaust survivors, were being deported to Germany as part of the ethnic cleansing of Germans from Czechoslovakia, which is a whole separate can of worms. Indeed there were even anti-Jewish pogroms in Czechoslovakia in 1948, mostly having to do with the restitution of property stolen by the Nazis. But Israel was, at the time, led by a Socialist coalition, and fighting highly reactionary Arab monarchies and Nazi collaborators in the Palestinian movement like the Mufti and some of his Husseini relatives. Britain was openly favoring the Arabs, selling them weapons, British officers even trained and commanded the Jordanian Arab legion, the only effective Arab fighting force of the Israeli War of Independence. The Arab Legion would go on to secure East Jerusalem and capture the regions of Judea and Samaria. Which were ethnically cleansed of their Jewish populations and annexed to Jordan, hence to be called the Transjordan and the region to be called the West Bank, until 1967. So if you could make some cash and screw with British interests in the Middle East, that was really a win-win for the Czechoslovakians.

A few years later, the selling of weapons to Israel would be used as a pretext for an antisemitic purge of the Czechoslovak Communist party. Jewish officials, despite very explicitly and obviously not being Zionists (membership in Communist or Zionist organizations was mutually exclusive), were purged, imprisoned, and even executed. The reason was internal politicking and bare simply hatred of Jews. Most of the people executed, being high ranking Communist officials were complicit and guilty of numerous crimes committed by the regime while they were in power, although those obviously weren't what they were on trial for.