After losing two sons, Judah faced a choice. The custom required his third and last surviving son, Shelah, to marry Tamar and try to raise up the line. Targum Pseudo-Jonathan on (Genesis 38:11) preserves Judah's decision in the exact words a grieving father might use.
He said to Tamar: Remain a widow in thy father's house, till Shela my son be grown up. The excuse sounds reasonable. Shelah was young. Let him grow. Let the family heal. But the Targum lets us hear what Judah was really thinking: Lest he also die as his brethren.
Judah did not believe Tamar was innocent. He believed she was a killer wife — what the later halakhah would call a katlanit, a woman who had buried two husbands and whose third marriage was forbidden by rabbinic caution (see Yevamot 64b). He had decided, in his grief, that the curse was with her. He was wrong. The curse had been with his own sons. But he did not know that, and he could not risk his last son on his uncertainty.
So he sent Tamar home. Technically a widow, practically abandoned. Waiting for a wedding that would never come. The Targumist writes with compressed sympathy: Tamar went and remained in her father's house. No argument. No protest. She walked home and she waited.
And while she waited, Judah's wife died. And Judah, older now, traveled up to the sheep-shearing in Timnah. And Tamar, tired of waiting for justice, decided to meet her father-in-law at the crossroads and take it for herself. The Targum is quietly setting up the most dangerous confrontation in Genesis — one that will produce the Messianic line through the will of a woman who refused to be erased.