How do both cartoons indicate the artists’ concern for workers?

how effective was it for the artists to depict standard oil as an octopus and title the other cartoon “the protectors of our industries”?

Each cartoon demonstrates the power of the Titans during the Gilded Age. In the first they are riding on the backs of the poor immigrants looking disheveled and weak and in the second the octopus is strangling the worker. Both present a view that the worker is being exploited or destroyed by the greed of the Titans. 
The octopus is appropriate imagery as it shows the varied reach of companies like Standard Oil. They were in control of the government, banks, workers, etc. The octopus is ominous and comes out of nowhere but is ultimately dangerous in how they can extend in many directions and can hold on tight making all in the grasp helpless.