Less malicious than that, a Telco isn't going to spend legal time/money/firepower on someone else.

I thought about that. What shady stuff though? Can't just be polluting or bribing politicians, can it?

Usually debatable accounting practices, shafting customers on a breath-taking scale (see Wells Fargo), but also pollution. Bribes were legalized by the CU ruling that literally legalized bribery of politicians, so no worries there.

No one wants the popo snooping, because if they try hard enough, they will find things.

It's simpler than that. The government wants access to the records, and they give telcos two options: The easy way or the hard way.