He was almost a victorious Senate candidate in Texas, and it's no coincidence that the other person with the most was his opponent. Context matters.
“He needed the fossil fuel money in order to almost (but still not) win his one campaign for statewide office” is probably not a defense the O'Rourke camp would be well served by when the issue, inevitably, arises.
When I donate to political campaigns as a private citizen who happens to be employed by a software company it does not suddenly make the campaign I donated to a shill for tech companies.
The usual approach to reporting political donations by firm/industry uses only PAC funds from corporate PACs controlled by firms in the industry, but OpenSecrets aggregates PAC and individual employee donations, which it justifies on the basis that “[o]ur research over more than 20 years shows a correlation between individuals' contributions and their employers' political interests and we have also observed that the donors we know about, and especially those who contribute at the maximum levels, are more commonly top executives in their companies, not lower-level employees.” [0]
In any case, I've been commenting on the political impact, not the merits, of the donations wet his candidacy.