If you are walked, you should get booked by the hotel that pushed you out and compensated:
If for some reason we’re unable to honor your reservation, we’ll pay for your accommodations that night at a nearby hotel and compensate you for the inconvenience. To be eligible, you must provide your Marriott Rewards membership number when making a reservation. Compensation varies by hotel brand.
The specifics are at Marriott® Elite Member Benefits and Guarantees, but you should get the new "comparable" room at a "comparable hotel" plus $200 (or 90,000 or 140,000 points) or $100 (or 90,000 points) as additional compensation. The hotel should pay for your stay at a nearby hotel, which means the rate should be paid by the hotel, even if more.