For instance, divide will be relatively low frequency as it tends to produce fractions which Nerdle can't cope with, and on the assumption that they will tend not to have three-digit numbers that limits the use of multiply as well, the format favours + & -. So on that basis one might leave divide to line 3 and maybe multiply in line 2, and hope that you get enough +- in the first line as not to have to worry about them.

0 will be quite rare as the rules say it can't be used as a leading digit, and is very unlikely to be used as a single digit.

Also

the Newcomb-Benford law suggests that we're more likely to get 1 as the first digit of a multi-digit number. If you're doing 2 operators then you presumably will have single digits to the left of the = and only have a double digit number as the answer, so it makes sense to have it as 1x. And in general lower numbers are more likely as the first digit of 2-digit numbers.