When the over-driven hyperdrive on their mobile shipyard burned out, the Chhrt'ktk't abandoned it in an inhabited system along their path, hoping it would work as a decoy to buy them more time to escape the Khreetan fleet pursuing them.
They didn't anticipate how far the pre-spacefaring species they turned over their broken-down maintenance facility to would subvert their plan.
Alex Holder, a retired engineer, just happened to be in the right place, at the right time, with the right mindset, to find himself chosen by the Chhrt'ktk't to hand over control of their shipyard to, simply because he was the first person they found able to interface with it. The Chhrt'ktk't could not possibly anticipate what he would do with it. And neither would anyone else.