It is very difficult to understand some Left alliances except in terms of pure expediency (collecting support under an arbitrary umbrella) - yet I find expediency inadequate as an explanation, since it would imply a need to ally with those whose sociopolitical aims are, if not in exact agreement, then at least not in irreconcilable opposition.
So that the 'Respect' political party in the UK is hard to comprehend ideologically:
And in more general terms it is hard to understand how Leftist support for 'Palestine' has become the primary article of foreign policy.
(Palestine is a litmus test for radical Leftism - despite its being an entity which does not feature as such on recent maps - and on older modern maps merely as a name for the British mandate; after which (in 1947) it was divided into a Jewish homeland of Israel and an Arab homeland of Jordan. Strictly, then, Jordan is Palestine, as the Left means the word. Perhaps, when they say they want an Arab state called Palestine, the Leftists merely mean that Jordan should change its name back to Palestine and accept the displaced Arab refugees who have been living in camps since 1948? Only kidding...)
The alliance between aggressively secular Trotskyite International Communists and conservative non-Christian religious of whatever type is hard to understand ideologically.
But it struck me that the unifying factor is perhaps being anti-Christian.
This not really operating at a personal level, but as a consequence of historical logic.
Leftism being a Christian Apostasy...
(Leftism being - in evolutionary terms - the end result of progressively discarding more and more Christian doctrine until only a distorted and partial sample of Christian ideas remain - which have also been translated into material proxies e.g. translating the spiritual ideal of love (charity, agape) into the material proxy of egalitarianism...)
...it seems natural that the Left be inclined to ally itself with any who share a hostility to Christianity.
Arguably that has been a broad historical pattern.
The party of Christian apostasy has always been on the Left; and it is perhaps understandable for the Left to form tactical groupings with any who are who are hostile to Christianity, for various different reasons.
(This anti-Christian group including, of course, mainstream, politically correct 'liberal' Christians - who are monolithically Leftist and perhaps the group which is most actively hostile to real Christianity; since they have the most immediately to gain from displacing real Christians - in terms of access to enhanced status, power, jobs, resources etc).
If so, alliances such as 'Respect' can be conceptualized as tactical anti-Christian alliances - not strategic ruling coalitions - and are held together by a negative ideology, not a positive shared goal.
Which unobvious negativeness may explain why the combination seems superficially incoherent and incomprehensible.