Even though contemporary leftism doesn't explicitly identify itself as a religion, it contains many beliefs that are either fundamentally unprovable or which have been disproven, or which blatantly contradict each other, yet liberals follow them at least as closely (and behave just as extremely as a result) as some people do when following their religion. To name just a few examples:
1. A belief in the existence of 47 [sic] genders.
2. A belief in the "gender wage gap" which has not only been thoroughly discredited for decades, it also makes little sense for someone to believe in a "wage gape" if they also believe that gender is an insignificant social construct.
3. A belief that a double standard is warranted between Christians and Muslims, the latter being allowed to explicitly do what is forbidden to Christians (including sidestepping the separation between church and state) with no provably rational justification.
I could go on but I think my point is clear. Liberalism is treated by many of its adherents like a religion, even though its foundational arguments are equally impossible to prove or may have been disproven. The fact that some variety exists between the extreme forms of liberalism is not so different from the variety that exists between different religious groups that identify by similar names. Liberalism is often a religion in everything but name and yet it not only sidesteps the separation between church and state, it receives massive government subsidy and endorsement.
This also may be part of why liberalism generally has the upper hand over western "conservatism"; Christianity is in many ways just another philosophy but it is a banned philosophy that undergirds many conservative groups, whereas the by now deeply religious philosophy of western liberalism that undergirds liberal parties is not banned but is subsidized and endorsed. This is not a fair situation.