The explanation is as below
As the second part of the structure refers to 'likelihood', we need 'greater'. 'greater' is used when the noun is a number. For example: percentage, rate, likelihood, distance and population.
Also, 'likelihood' means 'the probability of a specified outcome'. Thus, it's imprecise to say they had a likelihood/probability of coronary disease. The correct usage should be "likelihood of having coronary disease'.
why cant we say
the more coffee these doctors drank, the more was their likelihood of having coronary disease
why we need to accept below usage
the more coffee these doctors drank, the greater was their likelihood of having coronary disease
can likelihood of having a disease usage is correct? Please explain?