My first in-laws emigrated to Palestine in the early 1930s.
Father in law from Vienna via HaShomer HaTzair (despite being frum). MIL from northern Germany with her younger brother via Youth Aliyah.
Yes, their journeys and entry were facilitated by Zionists.
FIL, was a Zionist from a young age. His parents got Visas for the US in 1932, he refused to go with them, insisting on moving to Palestine.
Your generalization about those who came pre1948 is far from accurate.
I also had cousins from Brooklyn who arrived in the Yishuv in 1933 and 1946 via the Zionist organizations.
By 1946 it was virtually impossible to get permanent housing if you did not arrive through organized Zionist channels. Those arriving illegally lived clandestinely til May 1948.
As a side note I laugh at the right wing frum Jews in America complaining about illegal immigrants when so many of us were illegal immigrants in British Mandat Palestine. Talk about hypocrisy