Excel does display 0.00E+00 when we try to format that value as Scientific.
But I suspect that the coefficient is an even larger 'non-normalized' value. '2E+308' might be rounded from 1.79769313486232E+308, the largest 'normalized' value that Excel can calculate.
This is evident when we try to format the trendline label as Scientific with 14 decmal to display more precision. Second, the coefficients of the exponential trendline - especially '2E+308' - are misleading, if not bogus. It is important to explain that your dates are in the MDY form.
