That just seems incorrect.

Three valid constructions seem to fit here:

• J’ai encore du mal à m’expliquer que ces maudits trolls russes aient complètement fait chou blanc (que + subjonctif)
• J’ai encore du mal à m’expliquer comment ces maudits trolls russes ont complètement fait chou blanc (comment + indicatif, more neutral)
• J’ai encore du mal à m’expliquer comment ces maudits trolls russes auraient complètement fait chou blanc (comment + conditionnel, expresses more doubt)

But you can’t mix “comment” and “que” this way. In very familiar (childish) language, you might meet something like “comment qu’il a fait ?”, but in this context, it would still be followed by a conditionnel or an indicatif, not a subjonctif (comment qu’ils auraient / comment qu’il ont)

One sentence that would most look like the one shown would be “J’ai encore du mal à m’expliquer que ces « maudits troll russes », qui auraient essayé de s’immiscer dans la campagne présidentielle d’Emmanuel Macron pour la faire capoter, aient complètement fait « chou blanc »”.

Using the other construct with “comment” + “ont” works too, but with “comment” + “auraient” it is uglier here because you would have two “auraient” in a row. (the first one also expresses doubt, about the reality of the trolls, as opposed as if you write “qui ont essayé de s’immiscer”, which is also correct).

As a side note, the final interrogation mark is incorrect as well. It is not a direct question, so no such punctuation mark is expected.

The “correct” sentence could be:

J’ai encore du mal à m’expliquer comment ces « maudits troll russes » qui auraient essayé de s’immiscer dans la campagne présidentielle d’Emmanuel Macron pour la faire capoter ont complètement fait « chou blanc » ?

The problem with this is that the subject (maudits trolls russes) and the verb (faire chou blanc) are separated by a very long clause (qui auraient essayé de s’immiscer dans la campagne présidentielle d’Emmanuel Macron pour la faire capoter). The speaker probably felt it would be clearer to reinject the subject near the verb in the form of ils.

Now the first verbal group avoir du mal à s’expliquer can be used both with comment (e.g. j’ai du mal à m’expliquer comment il a fait ça) and que (e.g. j’ai du mal à m’expliquer qu’il fasse si chaud). Here you have the two constructions, first with comment and then with que. It doesn’t strike me as incorrect in a spoken, looser style.

As for the final question mark, it’s in line with the meaning and the sentence can be seen as a constructio ad sensum.

This sentence is a mess!

• First, it’s not a direct question but an indirect one.
• As the sentence stand there is no verb for “maudits trolls russes”.
• If we try to make “maudits trolls russes” the subject of one of the verbs we end up in problems without solutions, all pointing to the inanity of the speaker’s thinking.
• Patching up of this sentence calls for changing the verbs as they do not correspond to real life situations and as well it calls for making up expressions.

It si a sentence that shows clearly that the person speaking or writing uses French as a non literate French speaker or as a foreign and wreckless speaker; the basic organisation of ideas is chaotic, it is not even certain that they know what they are trying to say themselves and I’d suspect that their real motivation is merely the will to appears as if saying something, as long as they give the impression they know what they are talking about.

« Du mal à comprendre … qu’ils aient fait chou blanc » ? — What understanding does this person have of the fiscibility of such an operation, of a would-be quasi ineluctability with which they succeed ? (That’s what the words imply.) Engineers know that and at that they are engineers specialised in the field of security, not communicating anything of their knowledge to the press. Therefore, we don’t know what to do with this idea: if it is genuine we are dealing with a nitwit communicating to us states of affairs that have no reality—How can we go on reading ?—, and if it is not genuine then what can be this idea that has been formulated in a faulty manner ?

« Du mal à comprendre … comment ces maudits troll russes auraient essayé » ? — If the verb is taken to be “essayer de s’immiscer” (removal of “qui” which is then considered a fault) the same reasoning applies: the speaker is asking questions that are much too big for their understanding.

We are inclined to think, out of giving credit to the lesser of two evils, that what has not been understood is the possibility itself of a Russian criminal organisation interfering with French politics at the highest level; that is reasonnable. Nevertheles, this point of view leads to a solution only at the price of changing verbs and on top of that a dangling idea is left in the sentence, that of the lack of success, as there is then nothing said about it; we can’t tell for that person what are their feelings and thoughts about it. They could be glad it failed, not surprised, wondering how the criminals were made to fail, and so on. There is no way to patch up this sentence. We can do a bit of inventing for the missing part;

• J’ai du mal à accepter que ces maudits troll russes aient eu les moyens d’essayer de s’immiscer dans la campagne présidentielle d’Emmanuel Macron pour la faire capoter, c’est heureux qu’ils aient fait chou blanc.