Why didn't the iceberg in One Piece directly destroy Pluto's design?

Bruto's design drawings were designed by his master Tom, which is of special significance to him, understand? This is the great design of Tom's studio. You know, Iceberg and Francci respect Tom very much, and they don't want to destroy it. Moreover, this is also a plot setting. After Luffy helped Francci so much, Francci is willing to be his crew ~