What IBM noticed (or rather Louis V. Gerstner did) was that companies didn't buy computers to do payroll, they bought solutions to solving the payroll problem,

What IBM noticed (or rather Louis V. Gerstner did) was that companies didn't buy computers to do payroll, they bought solutions to solving the payroll problem, which happened to eventually be computers. And IBM were going broke trying to sell their computers instead of the best solutions, which they changed: even if that was on competitor's hardware or software.