~14% of Black people are Evangelicals. 12% of Black people voted Republican in 2020.
I'd hazard a guess that those two groups have significant overlap.
There are a few reasons why this assumption is not as fair to make as you would think it is:
1) The estimated share of black voters/people who identify as Republicans and Evangelical, respectively, varies depending on several different studies. The partisan figures you cited are from CNN/Edison's exit poll. However, other post-2020 election surveys place the number of black voters who voted for Donald Trump slightly lower - specifically, NYT/AP places Trump's black vote share at 8%, and the American National Election Studies (ANES) puts the two-party figure at 7.2%. Precinct data from overwhelmingly black (90%+) neighborhoods also places the Republican vote share within the single digits, which would lend more credence to the latter figures (of course, as ER pointed out, it is possible that black voters in less racially homogenous neighborhoods could be more Republican, so this is difficult to determine). Similarly, the estimates for the number of black people who identify as Evangelical is also debatable. The Public Religious Research Institute (PRRI), an organization that tracks various religious statistics, estimates that the share of black people who self-identify as Evangelical is 35% - much higher than the 14% from the Pew Research survey you cited. Also, as Del Tachi noted, Pew's methodology is likely lowballing these numbers because they include several denominations and vague denominational responses in the "Historical Black Protestant" churches category that they would otherwise categorize as Evangelical if the survey respondent were white (you can read more about this methodology
here). Mathematically, at least, this information suggests there is much more overlap between black Democrats and black Evangelicals.
2) It's also important to note that there are unique demographic patterns among black voters that would suggest that high levels of religiosity do not necessarily correlate with voting more Republican as with other racial/ethnic groups - and may even lend support to the contrary. Specifically, both major exit polls and ANES show black voters have an unusual political age gap where voters under 45 are more Republican than voters 45 and older. The most strongly Republican demographic, according to these data sets, was 30-44-year-old black voters, and the oldest cohort (60+ or 65+-year-old black voters, depending on the survey) was the most Democratic based on 2020 presidential vote. Based on your presupposition, one would expect that the 30-44 group would have a higher level of religiosity. However, the ANES survey data indicated that the 30-44 group were more likely to identify as religious "nones" than the oldest group and were less likely to attend church regularly or believe the Bible is literally the word of God.
Pew also found a similar pattern in their study of black religious identity by generation where the percentage of black people who identify as religiously unaffiliated in the Gen Z and Millennial Generations far surpasses those who identify as unaffiliated in the Boomer and Silent cohorts. This makes sense considering the historical linkage between black churches and the Democratic Party since the Civil Rights era in terms of boosting black turnout and providing support for establishment Democratic candidates. One can surmise that the high church attendance rates and overall religiosity of older black voters have made them one of the strongest Democratic constituencies, while the modestly more Republican leanings of some black voters under 45 could be a function of being less proximate to these institutions.
Even if you want to split hairs about what constitutes Evangelical or the size of this group among black Democrats, it is still evident from the information above that a significant share of black Democrats maintains high levels of religiosity while simultaneously being one of the most strongly Democratic constituencies.
(Btw, I can provide sources for all of these if you want, but I'm too tired and lazy to link rn.)
Poll
