It was a badly expressed point, but it's not a bad one.
I'm not sure what's facile about supposing that lawmakers are willing to compromise on reducing load on the court system. I don't understand how someone would find that motivation "more weird" than thinking that a controlling share of lawmakers are "ideologically committed" to bringing about the exact status quo we find ourselves in. If anything, I find your explanation to be the facile one. Simple explanations are emotionally appealing; simple explanations that scapegoat some disliked group of people are especially emotionally appealing.
Your particular explanation has two flaws, however:
(a) If conservatives really had their way, this isn't where we would have ended up. This is a compromise, or at least a counter-response to the state of affairs where there are so many implied obligations, warranties, and disclosures--a state of affairs that conservatives don't seem to support in the first place--that people need to sign or agree to 20-page legal documents as often as they do throughout the course of their lives.
A couple concrete examples:
* Most commercial software EULAs require you to agree that not to use the software to run nuclear reactors, because if that wasn't in there, and you used it to run a nuclear reactor, and it crashed, you and everyone who got radiation poisoning would take the software company to court and that would be a stupid waste of time, so to countervent that, we have EULAs that specifically call out that use case as not supported.
* Every apartment lease I have signed has a clause that forbids me from subletting the apartment, because otherwise, I would have an implied legal right to sublet my apartment. If that implied legal right didn't exist, that would be one fewer clause that I would have to read and initial when I rented an apartment.
Conservatives aren't and weren't the ones imposing those obligations in the first place. But, now that they exist, there are very long legal documents that people have to agree to. And, as it happens, when there's a dispute over whether either side has held up their end of a long legal document, it ends up in court and everything is expensive. Arbitration is a reaction to that, and since US law tends to operate in a "permitted unless explicitly prohibited" way, there wasn't necessarily any particular ideological or political action required to make mandatory arbitration possible in the first place (although if you know of any, please share).
(b) Given that this is a compromise, why is it a relatively stable compromise? Why doesn't it just get overturned or outlawed in every US state where Democrats control the state government? Two of those states are Delaware and California, for example, and since a lot of companies operate in California and incorporate in Delaware, the laws of those two states would have an outsized impact on the rest of the country.
I can think of one reasonable explanation: Democratic lawmakers in these states understand that the court system doesn't even have the capacity to handle all the litigation that it would need to handle without mandatory arbitration in place, so they maintain the shitty compromise and try to gradually angle for a more sustainable solution to the problem.
(Since we're not discussing conspiracy theories, I'm not going to touch the notion that Delaware and California Democrats are secretly corporatist "starve-the-beast" conservatives and that the two-party system is a sham.)