I was wondering about the grammatical reason(s) whereby a(n expected) genitive gerund/gerundive is sometimes replaced by an infinitive. Here are some representative examples of this phenomenon:
postero die consilium ceperunt ex oppido profugere. (Caes. BG. 7, 26)
Frustra autem niti neque aliud se fatigando nisi odium quaerere extremae dementiae est; nisi forte quem inhonesta et perniciosa libido tenet potentiae paucorum decus atque libertatem suam gratificari. (Sal. Iug. 3)
Ceterum iuventus pleraque, sed maxume nobilium, Catilinae inceptis favebat; quibus in otio vel magnifice vel molliter vivere copia erat. (Sal. Cat. 17, 3).
Nunc corpora curare tempus est. (Liv. 21, 54, 2)
Sed si tantus amor casus cognoscere nostros et breuiter Troiae supremum audire laborem, quamquam animus meminisse horret luctuque refugit, incipiam. (Verg. Aen. 2.10)
Is it possible to find a unified explanation for the replacement of a(n expected) genitive gerund/gerundive by an infinitive, shown in the previous examples?
Is/are there any internal structural reason(s) in Latin grammar for this replacement? For example, is there any connection with those constructions where the infinitive has a sort of purpose/"target" meaning? E.g., cf. Reddere hoc, non perdere erus me misit (Pl. Pseud. 642) and Avidi committere pugnam (Ov. Met. 5, 75)? Or is the infinitive justified as a result of an abstract reanalysis from consilium ceperunt to constituerunt, from libido tenet to libet, from tempus est to tempestivum est, etc.? NB: unlike nouns (e.g. consilium), verbs (e.g. constituerunt) and adjectives (tempestivum) can typically take infinitives as arguments in a more direct way.
Is there any external cause involved (e.g. an influence from Greek)?
As discussed below with Kingshorsey, it seems that the grecism-based explanation is quite plausible for Virgil’s example. See Mayer (1999: 175):
"On the syntax of amor and the infinitive Servius said: cognoscendorum casuum et Graeca figura est (...) Servius seems correct in identifying this instance as a grecism, for ἔρως was constructed with the infinitive; to him there was nothing 'natural' about it, it was best accounted for as a figure and borrowed from Greek." (bold mine: Mitomino)
However, the alternative analogy-based explanation commented on and criticized by Mayer (1999: 175), the one attributed to Roland G. Austin, a distinguished commentator of Virgil, can be said to have the advantage of relating it with the reanalysis process also mentioned in my question, which can be useful when accounting for apparently different cases like the one involved in Caesar’s example, the one in the title: for example, it seems that Pinkster (2021: 212) attributes the presence of the infinitive profugere to the reanalysis from the analytic collocation (Noun + light Verb) consilium ceperunt to the synthetic verb constituerunt. It is also worth noting that Friedrich Kritz & Friedrich Berger (1848: 426-427), two German classical philologists, also mentioned the usage of this infinitive by relating analytic expressions (e.g. lubido tenet) to synthetic ones (e.g. lubet). I've seen that other scholars have had the same intuition when describing the usage of this infinitive.
It appears to be difficult to obtain a unified explanation of the replacement for all the cases mentioned above in my question (unsurprisingly, "splitters" often win the debate against "lumpers", at least descriptively speaking. Divide et impera!). However, it seems to me that the presence of the infinitive in all the examples above (the ones from Plautus and Ovid included) is motivated by the general fact that this non-finite form seems to communicate a sort of "target" meaning (I know it's a vague expression but I don't know how to express my intuition better...). Please feel free to share your thoughts/intuitions with me.