Tax deductible is a weird way of phrasing it. It's not like these software companies were counting their money at the end of the quarter, and then deciding to do R&D instead of paying taxes. They had already paid R&D expenses to build the product, which gained them revenue. Previously they weren't allowed to actualize the cost of R&D all at once, so the business could be losing money, and still have to pay taxes on top of the loss (which is nuts).
This fixes the problem, so now if you spend $100 on software developers, and you make $100 from the software, then you have $0 income, instead of $80 income.
It was also weird because people pay money on income (dividend, partner payment, SCorp share, etc.) anyway, so in a long term view this incentivized companies to keep fewer software engineers on staff.
It’s more about whether or not the company has taxable profits for that year (importantly these are not the same as real profits). I would read this article to understand more about how being forced to amortize tax deductions for expenses affects a business’s taxes.
