It is difficult to tell whether this 1837 change of the subjunctive were to the indicative was was intended or not. For other cases in the text where we have “as much as it was/were …”, there have been no changes with respect to was /were (although 𝓞 is not extant for any of these other cases):
We may also add here the phrase “inasmuch as it was/were …”, for which there is one example:
For this example, the 1920 LDS edition emended the were to was. As discussed under Alma 1:32, the earliest text favors were in the phrase “as it was/were possible”, with only one example of was (namely, in Mosiah 21:18, listed above). The critical text will, in each case, follow the earliest reading, thus “as much as it were in their power” here in Alma 52:13. For further discussion of the use of the subjunctive were in the Book of Mormon text, see under mood in volume 3.
Summary: Restore in Alma 52:13 the subjunctive were in “as much as it were in their power” (the reading of the earliest textual sources, including 𝓞).