Nico Rosberg retired as world champion in December just days after beating out team-mate Lewis Hamilton, leaving Mercedes to find a replacement at short notice with the majority of the grid's top drivers already contracted for 2017.
They eventually struck a deal with Williams, who agreed to release Bottas, and the Finn signed a one-year deal with Mercedes.
And deputy team principal Williams, whose father Frank founded the team, knows Mercedes have got more than just a fast driver.
"He was a big part of our ambitions but it is not right to stand in a driver's way when a seat like Mercedes comes along."
And Mercedes team boss Toto Wolff admitted that Williams drove a hard bargain when it came to negotiations.
"It wasn't always obvious for us that we would get Valtteri," Wolff said.
Toto Wolff: The dynamic between Valtteri and Lewis works 1769459887uQeNtMFy
"Clearly we understood that it would be a compromise for Claire to let him go.
"And we found a solution that allows Williams to continue to develop their capabilities and resources and strengthen the team mid-term and long-term."