Fiscal conservatism seems to wrap two things together, that really should be separate. One is fiscal responsibility: that whatever one spends, one should take in, i.e. a balanced budget. Even the most fiscal conservative however know that there are some times the GOV must spend money, for economic stimulus during a recession, etc so even a pure fiscally responsible politician would most likely have some exceptions to balanced budget, 0 deficit in 100% of situations. Still, a balanced budget and reduction in deficit is the goal.
The 2nd is ideology: that government is "too big" and must be made smaller. One of the ways to do that is to starve it: cut taxes to the extent that pretty standard things the government traditionally provides, is unaffordable.
I think people confuse the two.
You can have high taxes, and a balanced budget and a very health economy. In fact during the "good old days" of post war boom, both personal and corporate taxes were much higher than they are now. They did not harm the economy.
In the same way, you can cut taxes, but be financially irresponsible, as in the current case. They are cutting taxes, without balancing the budget, and also INCREASING spending in some areas, particularly the military. Defense is so large that we don't even know what they are doing. They lose/misplace millions on a regular basis.
The Republicans cut taxes first stating that it would stimulate the economy and that stimulated economy would replace the reductions in tax rates with an overall increased base (supply side economics/ aka voodoo economics). Before the tax cuts were enacted, economists explained why this would not really work.
https://itep.org/moodys-and-conservative-economists-agree-the-trump-corporate-tax-cut-is-not-helping-workers/ But, I don't think the Republicans care. All they really care about it a) helping the donor class, the people funding their party, their campaigns in a really crappy quid pro quo, and b) give a rational for cutting a whole slew of programs that personally benefit the average American, whom they seem to have contempt for.
We kind of know this, because Paul Ryan went on record about this, in 2017, before the tax cuts were official. If that was truly the reason for cutting these programs (the deficit), why pass tax cuts? The tax cuts are going to add over a trillion to the deficit. Simple answer: don't do the tax cuts which benefit the 0.01% of Americans?
https://www.washingtonpost.com/news/wonk/wp/2017/12/01/gop-eyes-post-tax-cut-changes-to-welfare-medicare-and-social-security/?noredirect=on&utm_term=.1294f18823d5