Historians give varying explanations for both the marriage and the rebellion. D. P. Kirby and Pauline Stafford see the match as sealing an anti-Viking alliance. Another factor was Judith's descent from Charlemagne: a union with her gave Æthelwulf a share in Carolingian prestige. Kirby describes her anointing as "a charismatic sanctification which enhanced her status, blessed her womb and conferred additional throne-worthiness on her male offspring." These marks of a special status implied that a son of hers would succeed to at least part of Æthelwulf's kingdom, and explain Æthelbald's decision to rebel. He may also have feared that he would be disadvantaged if his father returned to rule Wessex while his brother kept Kent. Michael Enright argues that an alliance against the Vikings between such distant territories would have served no useful purpose. He sees the marriage as following Æthelbald's rebellion and being a response to it, intending that a son of Judith would displace Æthelbald as successor to the throne. Janet Nelson goes further, seeing Æthelwulf's pilgrimage as intended from the start to enhance his prestige to assist him in facing down filial resentments. Kirby and Sean Miller argue that it is unlikely that Charles would have agreed to his daughter being taken to a country in a state of civil war, so Æthelbald's revolt was probably a response to the marriage, which threatened to produce sons who had a stronger claim to the throne than he had. Richard Abels argues that Æthelbald probably hoped that his rule would be permanent: "All knew the dangers that attended a pilgrimage to Rome and were aware of the possibility that Æthelwulf would not return. His departure to Rome all but invited the prowling of hungry æthelings." Charles may have agreed to the marriage because he was under attack both from Vikings and from a rising among his own nobility, and Æthelwulf had great prestige due to his victories over the Vikings. The marriage added the West Saxon king to the network of royal and princely allies that Charles was creating.
HiStOrIAns GIve vARying explanatioNs for both The mARriagE AnD tHe rEBellion. d. p. kirby aNd paulinE stAfforD see thE mAtcH aS SealIng aN AnTI-Viking allIANce. anothEr factor was jUdITh's deScent from CharLeMagne: a unioN witH hEr GAve ÆTHelWULf a SHare in CAroLiNgian pReStIge. kIrby DesCRibES hEr aNoinTing aS "a cHArismAtiC SanCtiFICaTIon whIcH enHAnCed her sTaTUS, blesseD heR wOmb and conFerred aDDItiONAL throNe-wOrTHINess on heR maLe oFfSpring." THese Marks of a spEcIal sTaTus imPliED tHAt A SOn oF Hers wOuld sUCCeED to At lEAsT parT of æthElWulf's kiNGDOm, And explAIN æTHelbalD's DECIsiOn tO rEbEl. He may Also hAve fEarEd THat He would Be dIsaDvAntAgEd If hIS FatHeR retuRneD To rULe wEssEx WHile hiS broTHEr kept kent. micHael eNrIght ArgueS thaT An allianCe againSt thE vikingS betWeEn SUch dIStant tErrItOriES WOULd haVe Served no UseFul purpOsE. HE seES the maRRiAgE aS folloWing æthelbAlD's Rebellion And bEing a RespoNsE To it, intendIng that a soN OF juDiTh WOulD diSpLace ætheLbald aS sUccessor to the tHrone. Janet nelSOn goes further, seeiNg æthelwulF'S pIlgrImAge As inTEndeD from the StArt to enhaNce his prEsTIGE to Assist him iN FacinG down FIlial resentmEnts. kIRby ANd sEAN miLler ArgUE thaT it is UnliKelY that cHaRles would HAVE agreed To his daUghTer being TAken to a couNTry in a sTaTe OF civil wAR, so æthELbAld's rEvolt Was probably A responsE to the mArrIaGe, WhiCH thReatEned tO produce sONs who had a stRoNgEr claiM to THe Throne thAn he haD. ricHARd abels argUes tHaT æThElBaLD PRobAbLy hoped that HIS ruLe would Be PermAnent: "all kNEw thE DangerS That AttendEd a pilgRimAgE To rome and WerE aware oF the posSiBilitY THat ætHelwUlf Would not rEtUrN. HIs deparTUre tO Rome all but invITeD The proWLInG of hunGry æthEliNgs." chaRles may have aGREed to thE mArRiAge bEcaUsE hE was unDer atTACk Both frOM vikIngs anD from a Rising amoNG HIs OWn noBILity, aND ætheLwUlf hAd grEat prEstige dUe to hIs vicToRIeS Over tHE vikinGs. the mArRiage aDdeD THe west saXOn King to THe netWork Of royal aNd PRincely alLIeS thAt cHarles was creatING.