Interpretation controlling for industries

#1
Hello,
I'm doing a master thesis on the effect of CSR contracting on CSR performance. My model is based on a multiples regression by OLS.
I have regressed CSR level on CSR contracting and used several control variables and get as a results CSR contracting significant for p<0,1
Afterwards, I have add the control variables industries and created dummies for each industry and used the command i.industries in stata.
After controlling for industries, CSR contracting variable (independant variable) more significant than in the first regression, it's is now significant
for p<0,01. I'm struggling to understand the reasoning behind this big change of results. Could someone help me interpret why integrating
industry as a control variable has this big effect.
Thank you very much
Jamo