Several sentences, Help Plz

I need your kind help for this article lads >:), I found lotta of new phrase that difficult to understand...

1:.....had previously been focused only on the low end of the market were burrowing up to battle the.......

does burrow up mean raising up?

2:.....to attract the cream of China's fast-growing cohort of midlevel consumers......

cohort of... it sounds sooo odd, is it a common usage? and cream here is referred to?

3:The phrase can be similarly applied to middle market players in China that have been able to steal a march on incumbents by developing and releasing good enough products that are displacing premium ones.

what does "to steal a march on incumbents" mean? I don't really understand this.

Thanks >:)

"does burrow up mean raising up?"

To burrow would be to dig tunnels underground. So, yeah, it's like to rise up.

"cohort of... it sounds sooo odd, is it a common usage? and cream here is referred to?"

Cohort is friend, accomplice. I guess, it's fairly common. It's not obscure. Cream is referring to the idion, 'cream of the crop,' which is like the best of the a batch/group or whatever. So 'cream' is referring to best.

"what does "to steal a march on incumbents" mean? I don't really understand this."

Yeah, that's weird phrasing, but I suppose they are trying to say that the 'middle market players' have sort of taken or bullied their way into competition with the 'incumbents.' Shear force of will and all that....