This is technically an "AHC" but whatever.
Another commentator beat me to it, but this has been discussed earlier here, and political historians usually hold that the key event was a meeting of Conservative MPs in 1922 to discuss continuing to support Lloyd George as Prime Minister. The Conservatives could have formed a government on their own. Instead there was the creation of the "National Party" formed by the elements of the Liberal and Conservative Parties that supported Lloyd George. By the way, legally the "Conservative Party" started by the dissidents was technically a new party, and the National Party the successor to the Conservative Party, not an unimportant point as the National Party got the Conservative Party resources, not least its funds. On the other hand the Asquithian Liberal Party legally continued the pre- World War I Liberal Party. As a new party, the Conservative Party always had long odds of wining or even coming in second in an election.
Churchill never considered joining the Conservative Party. It was a surprise when he opted for the Liberal Party over the Nats. And also Chamberlain, like much of the National Party leadership, originally was a Liberal. But the Conservative Party formed from the split was always considered to be a fringe and reactionary element and something of a joke, though granted opposition to the European Community and Union later gave it a lease on life, and it was always very different from the Conservative Party of Disraeli and Salisbury.