Turing is the easiest:
What is a computer? What isn't a computer? If you can't answer that question, you don't have a computer. The Church-Turing thesis is the invention of the computer.
Lovelace and Hopper are notable for paradigm shifts (as much as I hate the term) in what computers "are".
Lovelace invented computers because the essence of the computer is the ability to perform computations, not just calculations:
Lovelace published the first algorithm (Babbage obviously had to have written a few to design an analytical engine) and was the first person imagine computers as more than just a flexible calculator. In particular, she was the first to use a variable to represent anything beyond the intermediate/final step of a calculation: she was computing the 7th term of a series, so she used series/loop indices.
Hopper invented computers because a general-purpose computer is a computation machine with a human-friendly interface. A "smart" lightbulb that runs embedded linux isn't a "computer" (until modified).
Grace Hopper conceived of abstract programming in human-aligned languages, and invented A-0, the first "compiler" (her term; now we'd call it a linker). Before Hopper, computers were only ever programmed directly in machine code; every step of a computer program was a specific operation. Before A-0, we just had computation machines, but no human-centered interface. After A-0, we had computers.
Zuse would be a perfectly excellent 5th name, as would Church, Godel, Herbrand, Bohm, and many others.